/* $Procedure ZZSPKAP1 ( S/P Kernel, apparent state ) */
/* Subroutine */ int zzspkap1_(integer *targ, doublereal *et, char *ref,
doublereal *sobs, char *abcorr, doublereal *starg, doublereal *lt,
ftnlen ref_len, ftnlen abcorr_len)
{
/* Initialized data */
static logical first = TRUE_;
static char flags[5*9] = "NONE " "LT " "LT+S " "CN " "CN+S " "XLT "
"XLT+S" "XCN " "XCN+S";
static char prvcor[5] = " ";
/* System generated locals */
integer i__1;
doublereal d__1;
/* Builtin functions */
integer s_cmp(char *, char *, ftnlen, ftnlen);
/* Subroutine */ int s_copy(char *, char *, ftnlen, ftnlen);
/* Local variables */
char corr[5];
extern /* Subroutine */ int zzspksb1_(integer *, doublereal *, char *,
doublereal *, ftnlen);
static logical xmit;
extern /* Subroutine */ int vequ_(doublereal *, doublereal *);
integer i__, refid;
extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
ftnlen, ftnlen), moved_(doublereal *, integer *, doublereal *);
static logical usecn;
doublereal sapos[3];
extern /* Subroutine */ int vsubg_(doublereal *, doublereal *, integer *,
doublereal *);
static logical uselt;
extern doublereal vnorm_(doublereal *), clight_(void);
extern integer isrchc_(char *, integer *, char *, ftnlen, ftnlen);
extern /* Subroutine */ int stelab_(doublereal *, doublereal *,
doublereal *), sigerr_(char *, ftnlen), chkout_(char *, ftnlen),
stlabx_(doublereal *, doublereal *, doublereal *);
integer ltsign;
extern /* Subroutine */ int ljucrs_(integer *, char *, char *, ftnlen,
ftnlen), setmsg_(char *, ftnlen);
doublereal tstate[6];
integer maxitr;
extern /* Subroutine */ int irfnum_(char *, integer *, ftnlen);
extern logical return_(void);
static logical usestl;
extern logical odd_(integer *);
/* $ Abstract */
/* Deprecated: This routine has been superseded by SPKAPS. This */
/* routine is supported for purposes of backward compatibility only. */
/* Return the state (position and velocity) of a target body */
/* relative to an observer, optionally corrected for light time and */
/* stellar aberration. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* SPK */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* TARG I Target body. */
/* ET I Observer epoch. */
/* REF I Inertial reference frame of observer's state. */
/* SOBS I State of observer wrt. solar system barycenter. */
/* ABCORR I Aberration correction flag. */
/* STARG O State of target. */
/* LT O One way light time between observer and target. */
/* $ Detailed_Input */
/* TARG is the NAIF ID code for a target body. The target */
/* and observer define a state vector whose position */
/* component points from the observer to the target. */
/* ET is the ephemeris time, expressed as seconds past J2000 */
/* TDB, at which the state of the target body relative to */
/* the observer is to be computed. ET refers to time at */
/* the observer's location. */
/* REF is the inertial reference frame with respect to which */
/* the observer's state SOBS is expressed. REF must be */
/* recognized by the SPICE Toolkit. The acceptable */
/* frames are listed in the Frames Required Reading, as */
/* well as in the SPICELIB routine CHGIRF. */
/* Case and blanks are not significant in the string REF. */
/* SOBS is the geometric (uncorrected) state of the observer */
/* relative to the solar system barycenter at epoch ET. */
/* SOBS is a 6-vector: the first three components of */
/* SOBS represent a Cartesian position vector; the last */
/* three components represent the corresponding velocity */
/* vector. SOBS is expressed relative to the inertial */
/* reference frame designated by REF. */
/* Units are always km and km/sec. */
/* ABCORR indicates the aberration corrections to be applied */
/* to the state of the target body to account for one-way */
/* light time and stellar aberration. See the discussion */
/* in the Particulars section for recommendations on */
/* how to choose aberration corrections. */
/* ABCORR may be any of the following: */
/* 'NONE' Apply no correction. Return the */
/* geometric state of the target body */
/* relative to the observer. */
/* The following values of ABCORR apply to the */
/* "reception" case in which photons depart from the */
/* target's location at the light-time corrected epoch */
/* ET-LT and *arrive* at the observer's location at ET: */
/* 'LT' Correct for one-way light time (also */
/* called "planetary aberration") using a */
/* Newtonian formulation. This correction */
/* yields the state of the target at the */
/* moment it emitted photons arriving at */
/* the observer at ET. */
/* The light time correction involves */
/* iterative solution of the light time */
/* equation (see Particulars for details). */
/* The solution invoked by the 'LT' option */
/* uses one iteration. */
/* 'LT+S' Correct for one-way light time and */
/* stellar aberration using a Newtonian */
/* formulation. This option modifies the */
/* state obtained with the 'LT' option to */
/* account for the observer's velocity */
/* relative to the solar system */
/* barycenter. The result is the apparent */
/* state of the target---the position and */
/* velocity of the target as seen by the */
/* observer. */
/* 'CN' Converged Newtonian light time */
/* correction. In solving the light time */
/* equation, the 'CN' correction iterates */
/* until the solution converges (three */
/* iterations on all supported platforms). */
/* Whether the 'CN+S' solution is */
/* substantially more accurate than the */
/* 'LT' solution depends on the geometry */
/* of the participating objects and on the */
/* accuracy of the input data. In all */
/* cases this routine will execute more */
/* slowly when a converged solution is */
/* computed. See the Particulars section */
/* of SPKEZR for a discussion of precision */
/* of light time corrections. */
/* 'CN+S' Converged Newtonian light time */
/* correction and stellar aberration */
/* correction. */
/* The following values of ABCORR apply to the */
/* "transmission" case in which photons *depart* from */
/* the observer's location at ET and arrive at the */
/* target's location at the light-time corrected epoch */
/* ET+LT: */
/* 'XLT' "Transmission" case: correct for */
/* one-way light time using a Newtonian */
/* formulation. This correction yields the */
/* state of the target at the moment it */
/* receives photons emitted from the */
/* observer's location at ET. */
/* 'XLT+S' "Transmission" case: correct for */
/* one-way light time and stellar */
/* aberration using a Newtonian */
/* formulation This option modifies the */
/* state obtained with the 'XLT' option to */
/* account for the observer's velocity */
/* relative to the solar system */
/* barycenter. The position component of */
/* the computed target state indicates the */
/* direction that photons emitted from the */
/* observer's location must be "aimed" to */
/* hit the target. */
/* 'XCN' "Transmission" case: converged */
/* Newtonian light time correction. */
/* 'XCN+S' "Transmission" case: converged */
/* Newtonian light time correction and */
/* stellar aberration correction. */
/* Neither special nor general relativistic effects are */
/* accounted for in the aberration corrections applied */
/* by this routine. */
/* Case and blanks are not significant in the string */
/* ABCORR. */
/* $ Detailed_Output */
/* STARG is a Cartesian state vector representing the position */
/* and velocity of the target body relative to the */
/* specified observer. STARG is corrected for the */
/* specified aberrations, and is expressed with respect */
/* to the specified inertial reference frame. The first */
/* three components of STARG represent the x-, y- and */
/* z-components of the target's position; last three */
/* components form the corresponding velocity vector. */
/* The position component of STARG points from the */
/* observer's location at ET to the aberration-corrected */
/* location of the target. Note that the sense of the */
/* position vector is independent of the direction of */
/* radiation travel implied by the aberration */
/* correction. */
/* The velocity component of STARG is obtained by */
/* evaluating the target's geometric state at the light */
/* time corrected epoch, so for aberration-corrected */
/* states, the velocity is not precisely equal to the */
/* time derivative of the position. */
/* Units are always km and km/sec. */
/* LT is the one-way light time between the observer and */
/* target in seconds. If the target state is corrected */
/* for aberrations, then LT is the one-way light time */
/* between the observer and the light time corrected */
/* target location. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If the value of ABCORR is not recognized, the error */
/* 'SPICE(SPKINVALIDOPTION)' is signaled. */
/* 2) If the reference frame requested is not a recognized */
/* inertial reference frame, the error 'SPICE(BADFRAME)' */
/* is signaled. */
/* 3) If the state of the target relative to the solar system */
/* barycenter cannot be computed, the error will be diagnosed */
/* by routines in the call tree of this routine. */
/* $ Files */
/* This routine computes states using SPK files that have been */
/* loaded into the SPICE system, normally via the kernel loading */
/* interface routine FURNSH. Application programs typically load */
/* kernels once before this routine is called, for example during */
/* program initialization; kernels need not be loaded repeatedly. */
/* See the routine FURNSH and the SPK and KERNEL Required Reading */
/* for further information on loading (and unloading) kernels. */
/* If any of the ephemeris data used to compute STARG are expressed */
/* relative to a non-inertial frame in the SPK files providing those */
/* data, additional kernels may be needed to enable the reference */
/* frame transformations required to compute the state. Normally */
/* these additional kernels are PCK files or frame kernels. Any */
/* such kernels must already be loaded at the time this routine is */
/* called. */
/* $ Particulars */
/* In space science or engineering applications one frequently */
/* wishes to know where to point a remote sensing instrument, such */
/* as an optical camera or radio antenna, in order to observe or */
/* otherwise receive radiation from a target. This pointing problem */
/* is complicated by the finite speed of light: one needs to point */
/* to where the target appears to be as opposed to where it actually */
/* is at the epoch of observation. We use the adjectives */
/* "geometric," "uncorrected," or "true" to refer to an actual */
/* position or state of a target at a specified epoch. When a */
/* geometric position or state vector is modified to reflect how it */
/* appears to an observer, we describe that vector by any of the */
/* terms "apparent," "corrected," "aberration corrected," or "light */
/* time and stellar aberration corrected." */
/* The SPICE Toolkit can correct for two phenomena affecting the */
/* apparent location of an object: one-way light time (also called */
/* "planetary aberration") and stellar aberration. Correcting for */
/* one-way light time is done by computing, given an observer and */
/* observation epoch, where a target was when the observed photons */
/* departed the target's location. The vector from the observer to */
/* this computed target location is called a "light time corrected" */
/* vector. The light time correction depends on the motion of the */
/* target, but it is independent of the velocity of the observer */
/* relative to the solar system barycenter. Relativistic effects */
/* such as light bending and gravitational delay are not accounted */
/* for in the light time correction performed by this routine. */
/* The velocity of the observer also affects the apparent location */
/* of a target: photons arriving at the observer are subject to a */
/* "raindrop effect" whereby their velocity relative to the observer */
/* is, using a Newtonian approximation, the photons' velocity */
/* relative to the solar system barycenter minus the velocity of the */
/* observer relative to the solar system barycenter. This effect is */
/* called "stellar aberration." Stellar aberration is independent */
/* of the velocity of the target. The stellar aberration formula */
/* used by this routine is non-relativistic. */
/* Stellar aberration corrections are applied after light time */
/* corrections: the light time corrected target position vector is */
/* used as an input to the stellar aberration correction. */
/* When light time and stellar aberration corrections are both */
/* applied to a geometric position vector, the resulting position */
/* vector indicates where the target "appears to be" from the */
/* observer's location. */
/* As opposed to computing the apparent position of a target, one */
/* may wish to compute the pointing direction required for */
/* transmission of photons to the target. This requires correction */
/* of the geometric target position for the effects of light time and */
/* stellar aberration, but in this case the corrections are computed */
/* for radiation traveling from the observer to the target. */
/* The "transmission" light time correction yields the target's */
/* location as it will be when photons emitted from the observer's */
/* location at ET arrive at the target. The transmission stellar */
/* aberration correction is the inverse of the traditional stellar */
/* aberration correction: it indicates the direction in which */
/* radiation should be emitted so that, using a Newtonian */
/* approximation, the sum of the velocity of the radiation relative */
/* to the observer and of the observer's velocity, relative to the */
/* solar system barycenter, yields a velocity vector that points in */
/* the direction of the light time corrected position of the target. */
/* The traditional aberration corrections applicable to observation */
/* and those applicable to transmission are related in a simple way: */
/* one may picture the geometry of the "transmission" case by */
/* imagining the "observation" case running in reverse time order, */
/* and vice versa. */
/* One may reasonably object to using the term "observer" in the */
/* transmission case, in which radiation is emitted from the */
/* observer's location. The terminology was retained for */
/* consistency with earlier documentation. */
/* Below, we indicate the aberration corrections to use for some */
/* common applications: */
/* 1) Find the apparent direction of a target for a remote-sensing */
/* observation. */
/* Use 'LT+S' or 'CN+S: apply both light time and stellar */
/* aberration corrections. */
/* Note that using light time corrections alone ('LT' or 'CN') */
/* is generally not a good way to obtain an approximation to */
/* an apparent target vector: since light time and stellar */
/* aberration corrections often partially cancel each other, */
/* it may be more accurate to use no correction at all than to */
/* use light time alone. */
/* 2) Find the corrected pointing direction to radiate a signal */
/* to a target. This computation is often applicable for */
/* implementing communications sessions. */
/* Use 'XLT+S' or 'XCN+S: apply both light time and stellar */
/* aberration corrections for transmission. */
/* 3) Compute the apparent position of a target body relative */
/* to a star or other distant object. */
/* Use 'LT', 'CN', 'LT+S', or 'CN+S' as needed to match the */
/* correction applied to the position of the distant */
/* object. For example, if a star position is obtained from */
/* a catalog, the position vector may not be corrected for */
/* stellar aberration. In this case, to find the angular */
/* separation of the star and the limb of a planet, the */
/* vector from the observer to the planet should be */
/* corrected for light time but not stellar aberration. */
/* 4) Obtain an uncorrected state vector derived directly from */
/* data in an SPK file. */
/* Use 'NONE'. */
/* C */
/* 5) Use a geometric state vector as a low-accuracy estimate */
/* of the apparent state for an application where execution */
/* speed is critical: */
/* Use 'NONE'. */
/* 6) While this routine cannot perform the relativistic */
/* aberration corrections required to compute states */
/* with the highest possible accuracy, it can supply the */
/* geometric states required as inputs to these computations: */
/* Use 'NONE', then apply high-accuracy aberration */
/* corrections (not available in the SPICE Toolkit). */
/* Below, we discuss in more detail how the aberration corrections */
/* applied by this routine are computed. */
/* Geometric case */
/* ============== */
/* SPKAPP begins by computing the geometric position T(ET) of the */
/* target body relative to the solar system barycenter (SSB). */
/* Subtracting the geometric position of the observer O(ET) gives */
/* the geometric position of the target body relative to the */
/* observer. The one-way light time, LT, is given by */
/* | T(ET) - O(ET) | */
/* LT = ------------------- */
/* c */
/* The geometric relationship between the observer, target, and */
/* solar system barycenter is as shown: */
/* SSB ---> O(ET) */
/* | / */
/* | / */
/* | / */
/* | / T(ET) - O(ET) */
/* V V */
/* T(ET) */
/* The returned state consists of the position vector */
/* T(ET) - O(ET) */
/* and a velocity obtained by taking the difference of the */
/* corresponding velocities. In the geometric case, the */
/* returned velocity is actually the time derivative of the */
/* position. */
/* Reception case */
/* ============== */
/* When any of the options 'LT', 'CN', 'LT+S', 'CN+S' is */
/* selected, SPKAPP computes the position of the target body at */
/* epoch ET-LT, where LT is the one-way light time. Let T(t) and */
/* O(t) represent the positions of the target and observer */
/* relative to the solar system barycenter at time t; then LT is */
/* the solution of the light-time equation */
/* | T(ET-LT) - O(ET) | */
/* LT = ------------------------ (1) */
/* c */
/* The ratio */
/* | T(ET) - O(ET) | */
/* --------------------- (2) */
/* c */
/* is used as a first approximation to LT; inserting (2) into the */
/* RHS of the light-time equation (1) yields the "one-iteration" */
/* estimate of the one-way light time. Repeating the process */
/* until the estimates of LT converge yields the "converged */
/* Newtonian" light time estimate. */
/* Subtracting the geometric position of the observer O(ET) gives */
/* the position of the target body relative to the observer: */
/* T(ET-LT) - O(ET). */
/* SSB ---> O(ET) */
/* | \ | */
/* | \ | */
/* | \ | T(ET-LT) - O(ET) */
/* | \ | */
/* V V V */
/* T(ET) T(ET-LT) */
/* The position component of the light-time corrected state */
/* is the vector */
/* T(ET-LT) - O(ET) */
/* The velocity component of the light-time corrected state */
/* is the difference */
/* T_vel(ET-LT) - O_vel(ET) */
/* where T_vel and O_vel are, respectively, the velocities of */
/* the target and observer relative to the solar system */
/* barycenter at the epochs ET-LT and ET. */
/* If correction for stellar aberration is requested, the target */
/* position is rotated toward the solar system barycenter- */
/* relative velocity vector of the observer. The rotation is */
/* computed as follows: */
/* Let r be the light time corrected vector from the observer */
/* to the object, and v be the velocity of the observer with */
/* respect to the solar system barycenter. Let w be the angle */
/* between them. The aberration angle phi is given by */
/* sin(phi) = v sin(w) / c */
/* Let h be the vector given by the cross product */
/* h = r X v */
/* Rotate r by phi radians about h to obtain the apparent */
/* position of the object. */
/* The velocity component of the output state STARG is */
/* not corrected for stellar aberration. */
/* Transmission case */
/* ================== */
/* When any of the options 'XLT', 'XCN', 'XLT+S', 'XCN+S' are */
/* selected, SPKAPP computes the position of the target body T at */
/* epoch ET+LT, where LT is the one-way light time. LT is the */
/* solution of the light-time equation */
/* | T(ET+LT) - O(ET) | */
/* LT = ------------------------ (3) */
/* c */
/* Subtracting the geometric position of the observer, O(ET), */
/* gives the position of the target body relative to the */
/* observer: T(ET-LT) - O(ET). */
/* SSB --> O(ET) */
/* / | * */
/* / | * T(ET+LT) - O(ET) */
/* / |* */
/* / *| */
/* V V V */
/* T(ET+LT) T(ET) */
/* The position component of the light-time corrected state */
/* is the vector */
/* T(ET+LT) - O(ET) */
/* The velocity component of the light-time corrected state */
/* is the difference */
/* T_vel(ET+LT) - O_vel(ET) */
/* where T_vel and O_vel are, respectively, the velocities of */
/* the target and observer relative to the solar system */
/* barycenter at the epochs ET+LT and ET. */
/* If correction for stellar aberration is requested, the target */
/* position is rotated away from the solar system barycenter- */
/* relative velocity vector of the observer. The rotation is */
/* computed as in the reception case, but the sign of the */
/* rotation angle is negated. */
/* The velocity component of the output state STARG is */
/* not corrected for stellar aberration. */
/* Neither special nor general relativistic effects are accounted */
/* for in the aberration corrections performed by this routine. */
/* $ Examples */
/* In the following code fragment, SPKSSB and SPKAPP are used */
/* to display the position of Io (body 501) as seen from the */
/* Voyager 2 spacecraft (Body -32) at a series of epochs. */
/* Normally, one would call the high-level reader SPKEZR to obtain */
/* state vectors. The example below illustrates the interface */
/* of this routine but is not intended as a recommendation on */
/* how to use the SPICE SPK subsystem. */
/* The use of integer ID codes is necessitated by the low-level */
/* interface of this routine. */
/* IO = 501 */
/* VGR2 = -32 */
/* DO WHILE ( EPOCH .LE. END ) */
/* CALL SPKSSB ( VGR2, EPOCH, 'J2000', STVGR2 ) */
/* CALL SPKAPP ( IO, EPOCH, 'J2000', STVGR2, */
/* . 'LT+S', STIO, LT ) */
/* CALL RECRAD ( STIO, RANGE, RA, DEC ) */
/* WRITE (*,*) RA * DPR(), DEC * DPR() */
/* EPOCH = EPOCH + DELTA */
/* END DO */
/* $ Restrictions */
/* 1) The kernel files to be used by SPKAPP must be loaded */
/* (normally by the SPICELIB kernel loader FURNSH) before */
/* this routine is called. */
/* 2) Unlike most other SPK state computation routines, this */
/* routine requires that the input state be relative to an */
/* inertial reference frame. Non-inertial frames are not */
/* supported by this routine. */
/* 3) In a future version of this routine, the implementation */
/* of the aberration corrections may be enhanced to improve */
/* accuracy. */
/* $ Literature_References */
/* SPK Required Reading. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* H.A. Neilan (JPL) */
/* W.L. Taber (JPL) */
/* B.V. Semenov (JPL) */
/* I.M. Underwood (JPL) */
/* $ Version */
/* - SPICELIB Version 3.1.0, 04-JUL-2014 (NJB) (BVS) */
/* Discussion of light time corrections was updated. Assertions */
/* that converged light time corrections are unlikely to be */
/* useful were removed. */
/* Last update was 21-SEP-2013 (BVS) */
/* Updated to call LJUCRS instead of CMPRSS/UCASE. */
/* - SPICELIB Version 3.0.3, 18-MAY-2010 (BVS) */
/* Index lines now state that this routine is deprecated. */
/* - SPICELIB Version 3.0.2, 08-JAN-2008 (NJB) */
/* The Abstract section of the header was updated to */
/* indicate that this routine has been deprecated. */
/* - SPICELIB Version 3.0.1, 20-OCT-2003 (EDW) */
/* Added mention that LT returns in seconds. */
/* Corrected spelling errors. */
/* - SPICELIB Version 3.0.0, 18-DEC-2001 (NJB) */
/* Updated to handle aberration corrections for transmission */
/* of radiation. Formerly, only the reception case was */
/* supported. The header was revised and expanded to explain */
/* the functionality of this routine in more detail. */
/* - SPICELIB Version 2.1.0, 09-JUL-1996 (WLT) */
/* Corrected the description of LT in the Detailed Output */
/* section of the header. */
/* - SPICELIB Version 2.0.0, 22-MAY-1995 (WLT) */
/* The routine was modified to support the options 'CN' and */
/* 'CN+S' aberration corrections. Moreover, diagnostics were */
/* added to check for reference frames that are not recognized */
/* inertial frames. */
/* - SPICELIB Version 1.1.2, 10-MAR-1992 (WLT) */
/* Comment section for permuted index source lines was added */
/* following the header. */
/* - SPICELIB Version 1.1.1, 06-MAR-1991 (JML) */
/* In the example program, the calling sequence of SPKAPP */
/* was corrected. */
/* - SPICELIB Version 1.1.0, 25-MAY-1990 (HAN) */
/* The local variable CORR was added to eliminate a */
/* run-time error that occurred when SPKAPP was determining */
/* what corrections to apply to the state. */
/* - SPICELIB Version 1.0.1, 22-MAR-1990 (HAN) */
/* Literature references added to the header. */
/* - SPICELIB Version 1.0.0, 31-JAN-1990 (IMU) */
/* -& */
/* $ Index_Entries */
/* DEPRECATED low-level aberration correction */
/* DEPRECATED apparent state from spk file */
/* DEPRECATED get apparent state */
/* -& */
/* $ Revisions */
/* - SPICELIB Version 2.0.0, 22-MAY-1995 (WLT) */
/* The routine was modified to support the options 'CN' and */
/* 'CN+S' aberration corrections. Moreover, diagnostics were */
/* added to check for reference frames that are not recognized */
/* inertial frames. */
/* - SPICELIB Version 1.1.1, 06-MAR-1991 (JML) */
/* In the example program, the calling sequence of SPKAPP */
/* was corrected. */
/* - SPICELIB Version 1.1.0, 25-MAY-1990 (HAN) */
/* The local variable CORR was added to eliminate a run-time */
/* error that occurred when SPKAPP was determining what */
/* corrections to apply to the state. If the literal string */
/* 'LT' was assigned to ABCORR, SPKAPP attempted to look at */
/* ABCORR(3:4). Because ABCORR is a passed length argument, its */
/* length is not guaranteed, and those positions may not exist. */
/* Searching beyond the bounds of a string resulted in a */
/* run-time error at NAIF because NAIF compiles SPICELIB using the */
/* CHECK=BOUNDS option for the DEC VAX/VMX DCL FORTRAN command. */
/* Also, without the local variable CORR, SPKAPP would have to */
/* modify the value of a passed argument, ABCORR. That's a no no. */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* Indices of flags in the FLAGS array: */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("ZZSPKAP1", (ftnlen)8);
}
if (first || s_cmp(abcorr, prvcor, abcorr_len, (ftnlen)5) != 0) {
/* The aberration correction flag differs from the value it */
/* had on the previous call, if any. Analyze the new flag. */
/* Remove leading and embedded white space from the aberration */
/* correction flag and convert to upper case. */
ljucrs_(&c__0, abcorr, corr, abcorr_len, (ftnlen)5);
/* Locate the flag in our list of flags. */
i__ = isrchc_(corr, &c__9, flags, (ftnlen)5, (ftnlen)5);
if (i__ == 0) {
setmsg_("Requested aberration correction # is not supported.", (
ftnlen)51);
errch_("#", abcorr, (ftnlen)1, abcorr_len);
sigerr_("SPICE(SPKINVALIDOPTION)", (ftnlen)23);
chkout_("ZZSPKAP1", (ftnlen)8);
return 0;
}
/* The aberration correction flag is recognized; save it. */
s_copy(prvcor, abcorr, (ftnlen)5, abcorr_len);
/* Set logical flags indicating the attributes of the requested */
/* correction. */
xmit = i__ > 5;
uselt = i__ == 2 || i__ == 3 || i__ == 6 || i__ == 7;
usestl = i__ > 1 && odd_(&i__);
usecn = i__ == 4 || i__ == 5 || i__ == 8 || i__ == 9;
first = FALSE_;
}
/* See if the reference frame is a recognized inertial frame. */
irfnum_(ref, &refid, ref_len);
if (refid == 0) {
setmsg_("The requested frame '#' is not a recognized inertial frame. "
, (ftnlen)60);
errch_("#", ref, (ftnlen)1, ref_len);
sigerr_("SPICE(BADFRAME)", (ftnlen)15);
chkout_("ZZSPKAP1", (ftnlen)8);
return 0;
}
/* Determine the sign of the light time offset. */
if (xmit) {
ltsign = 1;
} else {
ltsign = -1;
}
/* Find the geometric state of the target body with respect to the */
/* solar system barycenter. Subtract the state of the observer */
/* to get the relative state. Use this to compute the one-way */
/* light time. */
zzspksb1_(targ, et, ref, starg, ref_len);
vsubg_(starg, sobs, &c__6, tstate);
moved_(tstate, &c__6, starg);
*lt = vnorm_(starg) / clight_();
/* To correct for light time, find the state of the target body */
/* at the current epoch minus the one-way light time. Note that */
/* the observer remains where he is. */
if (uselt) {
maxitr = 1;
} else if (usecn) {
maxitr = 3;
} else {
maxitr = 0;
}
i__1 = maxitr;
for (i__ = 1; i__ <= i__1; ++i__) {
d__1 = *et + ltsign * *lt;
zzspksb1_(targ, &d__1, ref, starg, ref_len);
vsubg_(starg, sobs, &c__6, tstate);
moved_(tstate, &c__6, starg);
*lt = vnorm_(starg) / clight_();
}
/* At this point, STARG contains the light time corrected */
/* state of the target relative to the observer. */
/* If stellar aberration correction is requested, perform it now. */
/* Stellar aberration corrections are not applied to the target's */
/* velocity. */
if (usestl) {
if (xmit) {
/* This is the transmission case. */
/* Compute the position vector obtained by applying */
/* "reception" stellar aberration to STARG. */
stlabx_(starg, &sobs[3], sapos);
vequ_(sapos, starg);
} else {
/* This is the reception case. */
/* Compute the position vector obtained by applying */
/* "reception" stellar aberration to STARG. */
stelab_(starg, &sobs[3], sapos);
vequ_(sapos, starg);
}
}
chkout_("ZZSPKAP1", (ftnlen)8);
return 0;
} /* zzspkap1_ */
/* $Procedure SPKGPS ( S/P Kernel, geometric position ) */
/* Subroutine */ int spkgps_(integer *targ, doublereal *et, char *ref,
integer *obs, doublereal *pos, doublereal *lt, ftnlen ref_len)
{
/* Initialized data */
static logical first = TRUE_;
/* System generated locals */
integer i__1, i__2, i__3;
/* Builtin functions */
integer s_cmp(char *, char *, ftnlen, ftnlen), s_rnge(char *, integer,
char *, integer);
/* Local variables */
extern /* Subroutine */ int vadd_(doublereal *, doublereal *, doublereal *
);
integer cobs, legs;
doublereal sobs[6];
extern /* Subroutine */ int vsub_(doublereal *, doublereal *, doublereal *
), vequ_(doublereal *, doublereal *), zznamfrm_(integer *, char *,
integer *, char *, integer *, ftnlen, ftnlen), zzctruin_(integer
*);
integer i__;
extern /* Subroutine */ int etcal_(doublereal *, char *, ftnlen);
integer refid;
extern /* Subroutine */ int chkin_(char *, ftnlen);
char oname[40];
doublereal descr[5];
integer ctarg[20];
char ident[40], tname[40];
extern /* Subroutine */ int errch_(char *, char *, ftnlen, ftnlen),
moved_(doublereal *, integer *, doublereal *);
logical found;
extern /* Subroutine */ int repmi_(char *, char *, integer *, char *,
ftnlen, ftnlen, ftnlen);
doublereal starg[120] /* was [6][20] */;
logical nofrm;
static char svref[32];
doublereal stemp[6];
integer ctpos;
doublereal vtemp[6];
extern doublereal vnorm_(doublereal *);
extern /* Subroutine */ int bodc2n_(integer *, char *, logical *, ftnlen);
static integer svctr1[2];
extern logical failed_(void);
extern /* Subroutine */ int cleard_(integer *, doublereal *);
integer handle, cframe;
extern /* Subroutine */ int refchg_(integer *, integer *, doublereal *,
doublereal *);
extern doublereal clight_(void);
integer tframe[20];
extern integer isrchi_(integer *, integer *, integer *);
extern /* Subroutine */ int sigerr_(char *, ftnlen), chkout_(char *,
ftnlen);
static integer svrefi;
extern /* Subroutine */ int irfnum_(char *, integer *, ftnlen), prefix_(
char *, integer *, char *, ftnlen, ftnlen), setmsg_(char *,
ftnlen), suffix_(char *, integer *, char *, ftnlen, ftnlen);
integer tmpfrm;
extern /* Subroutine */ int irfrot_(integer *, integer *, doublereal *),
spksfs_(integer *, doublereal *, integer *, doublereal *, char *,
logical *, ftnlen);
extern integer frstnp_(char *, ftnlen);
extern logical return_(void);
doublereal psxfrm[9] /* was [3][3] */;
extern /* Subroutine */ int spkpvn_(integer *, doublereal *, doublereal *,
integer *, doublereal *, integer *), intstr_(integer *, char *,
ftnlen);
integer nct;
doublereal rot[9] /* was [3][3] */;
extern /* Subroutine */ int mxv_(doublereal *, doublereal *, doublereal *)
;
char tstring[80];
/* $ Abstract */
/* Compute the geometric position of a target body relative to an */
/* observing body. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* SPK */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Abstract */
/* This file contains the number of inertial reference */
/* frames that are currently known by the SPICE toolkit */
/* software. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* None. */
/* $ Keywords */
/* FRAMES */
/* $ Declarations */
/* $ Brief_I/O */
/* VARIABLE I/O DESCRIPTION */
/* -------- --- -------------------------------------------------- */
/* NINERT P Number of known inertial reference frames. */
/* $ Parameters */
/* NINERT is the number of recognized inertial reference */
/* frames. This value is needed by both CHGIRF */
/* ZZFDAT, and FRAMEX. */
/* $ Author_and_Institution */
/* W.L. Taber (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 10-OCT-1996 (WLT) */
/* -& */
/* $ Abstract */
/* This include file defines the dimension of the counter */
/* array used by various SPICE subsystems to uniquely identify */
/* changes in their states. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Parameters */
/* CTRSIZ is the dimension of the counter array used by */
/* various SPICE subsystems to uniquely identify */
/* changes in their states. */
/* $ Author_and_Institution */
/* B.V. Semenov (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 29-JUL-2013 (BVS) */
/* -& */
/* End of include file. */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* TARG I Target body. */
/* ET I Target epoch. */
/* REF I Target reference frame. */
/* OBS I Observing body. */
/* POS O Position of target. */
/* LT O Light time. */
/* $ Detailed_Input */
/* TARG is the standard NAIF ID code for a target body. */
/* ET is the epoch (ephemeris time) at which the position */
/* of the target body is to be computed. */
/* REF is the name of the reference frame to */
/* which the vectors returned by the routine should */
/* be rotated. This may be any frame supported by */
/* the SPICELIB subroutine REFCHG. */
/* OBS is the standard NAIF ID code for an observing body. */
/* $ Detailed_Output */
/* POS contains the position of the target */
/* body, relative to the observing body. This vector is */
/* rotated into the specified reference frame. Units */
/* are always km. */
/* LT is the one-way light time from the observing body */
/* to the geometric position of the target body at the */
/* specified epoch. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If insufficient ephemeris data has been loaded to compute */
/* the necessary positions, the error SPICE(SPKINSUFFDATA) is */
/* signalled. */
/* $ Files */
/* See: $Restrictions. */
/* $ Particulars */
/* SPKGPS computes the geometric position, T(t), of the target */
/* body and the geometric position, O(t), of the observing body */
/* relative to the first common center of motion. Subtracting */
/* O(t) from T(t) gives the geometric position of the target */
/* body relative to the observer. */
/* CENTER ----- O(t) */
/* | / */
/* | / */
/* | / */
/* | / T(t) - O(t) */
/* | / */
/* T(t) */
/* The one-way light time, tau, is given by */
/* | T(t) - O(t) | */
/* tau = ----------------- */
/* c */
/* For example, if the observing body is -94, the Mars Observer */
/* spacecraft, and the target body is 401, Phobos, then the */
/* first common center is probably 4, the Mars Barycenter. */
/* O(t) is the position of -94 relative to 4 and T(t) is the */
/* position of 401 relative to 4. */
/* The center could also be the Solar System Barycenter, body 0. */
/* For example, if the observer is 399, Earth, and the target */
/* is 299, Venus, then O(t) would be the position of 399 relative */
/* to 0 and T(t) would be the position of 299 relative to 0. */
/* Ephemeris data from more than one segment may be required */
/* to determine the positions of the target body and observer */
/* relative to a common center. SPKGPS reads as many segments */
/* as necessary, from as many files as necessary, using files */
/* that have been loaded by previous calls to SPKLEF (load */
/* ephemeris file). */
/* SPKGPS is similar to SPKGEO but returns geometric positions */
/* only. */
/* $ Examples */
/* The following code example computes the geometric */
/* position of the moon with respect to the earth and */
/* then prints the distance of the moon from the */
/* the earth at a number of epochs. */
/* Assume the SPK file SAMPLE.BSP contains ephemeris data */
/* for the moon relative to earth over the time interval */
/* from BEGIN to END. */
/* INTEGER EARTH */
/* PARAMETER ( EARTH = 399 ) */
/* INTEGER MOON */
/* PARAMETER ( MOON = 301 ) */
/* INTEGER N */
/* PARAMETER ( N = 100 ) */
/* INTEGER I */
/* CHARACTER*(20) UTC */
/* DOUBLE PRECISION BEGIN */
/* DOUBLE PRECISION DELTA */
/* DOUBLE PRECISION END */
/* DOUBLE PRECISION ET */
/* DOUBLE PRECISION POS ( 3 ) */
/* DOUBLE PRECISION LT */
/* DOUBLE PRECISION VNORM */
/* C */
/* C Load the binary SPK ephemeris file. */
/* C */
/* CALL FURNSH ( 'SAMPLE.BSP' ) */
/* . */
/* . */
/* . */
/* C */
/* C Divide the interval of coverage [BEGIN,END] into */
/* C N steps. At each step, compute the position, and */
/* C print out the epoch in UTC time and position norm. */
/* C */
/* DELTA = ( END - BEGIN ) / N */
/* DO I = 0, N */
/* ET = BEGIN + I*DELTA */
/* CALL SPKGPS ( MOON, ET, 'J2000', EARTH, POS, LT ) */
/* CALL ET2UTC ( ET, 'C', 0, UTC ) */
/* WRITE (*,*) UTC, VNORM ( POS ) */
/* END DO */
/* $ Restrictions */
/* 1) The ephemeris files to be used by SPKGPS must be loaded */
/* by SPKLEF before SPKGPS is called. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* B.V. Semenov (JPL) */
/* W.L. Taber (JPL) */
/* $ Version */
/* - SPICELIB Version 2.0.0, 08-JAN-2014 (BVS) */
/* Updated to save the input frame name and POOL state counter */
/* and to do frame name-ID conversion only if the counter has */
/* changed. */
/* Updated to map the input frame name to its ID by first calling */
/* ZZNAMFRM, and then calling IRFNUM. The side effect of this */
/* change is that now the frame with the fixed name 'DEFAULT' */
/* that can be associated with any code via CHGIRF's entry point */
/* IRFDEF will be fully masked by a frame with indentical name */
/* defined via a text kernel. Previously the CHGIRF's 'DEFAULT' */
/* frame masked the text kernel frame with the same name. */
/* Replaced SPKLEF with FURNSH and fixed errors in Examples. */
/* - SPICELIB Version 1.2.0, 05-NOV-2005 (NJB) */
/* Updated to remove non-standard use of duplicate arguments */
/* in VADD calls. */
/* - SPICELIB Version 1.1.0, 05-JAN-2005 (NJB) */
/* Tests of routine FAILED() were added. */
/* - SPICELIB Version 1.0.0, 9-JUL-1998 (WLT) */
/* -& */
/* $ Index_Entries */
/* geometric position of one body relative to another */
/* -& */
/* $ Revisions */
/* - SPICELIB Version 1.2.0, 05-NOV-2005 (NJB) */
/* Updated to remove non-standard use of duplicate arguments */
/* in VADD calls. */
/* -& */
/* This is the idea: */
/* Every body moves with respect to some center. The center */
/* is itself a body, which in turn moves about some other */
/* center. If we begin at the target body (T), follow */
/* the chain, */
/* T */
/* \ */
/* SSB \ */
/* \ C[1] */
/* \ / */
/* \ / */
/* \ / */
/* \ / */
/* C[3]-----------C[2] */
/* and avoid circular definitions (A moves about B, and B moves */
/* about A), eventually we get the position relative to the solar */
/* system barycenter (which, for our purposes, doesn't move). */
/* Thus, */
/* T = T + C[1] + C[2] + ... + C[n] */
/* SSB C[1] C[2] [C3] SSB */
/* where */
/* X */
/* Y */
/* is the position of body X relative to body Y. */
/* However, we don't want to follow each chain back to the SSB */
/* if it isn't necessary. Instead we will just follow the chain */
/* of the target body and follow the chain of the observing body */
/* until we find a common node in the tree. */
/* In the example below, C is the first common node. We compute */
/* the position of TARG relative to C and the position of OBS */
/* relative to C, then subtract the two positions. */
/* TARG */
/* \ */
/* SSB \ */
/* \ A */
/* \ / OBS */
/* \ / | */
/* \ / | */
/* \ / | */
/* B-------------C-----------------D */
/* SPICELIB functions */
/* Local parameters */
/* CHLEN is the maximum length of a chain. That is, */
/* it is the maximum number of bodies in the chain from */
/* the target or observer to the SSB. */
/* Saved frame name length. */
/* Local variables */
/* Saved frame name/ID item declarations. */
/* Saved frame name/ID items. */
/* Initial values. */
/* In-line Function Definitions */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("SPKGPS", (ftnlen)6);
}
/* Initialization. */
if (first) {
/* Initialize counter. */
zzctruin_(svctr1);
first = FALSE_;
}
/* We take care of the obvious case first. It TARG and OBS are the */
/* same we can just fill in zero. */
if (*targ == *obs) {
*lt = 0.;
cleard_(&c__3, pos);
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
/* CTARG contains the integer codes of the bodies in the */
/* target body chain, beginning with TARG itself and then */
/* the successive centers of motion. */
/* STARG(1,I) is the position of the target body relative */
/* to CTARG(I). The id-code of the frame of this position is */
/* stored in TFRAME(I). */
/* COBS and SOBS will contain the centers and positions of the */
/* observing body. (They are single elements instead of arrays */
/* because we only need the current center and position of the */
/* observer relative to it.) */
/* First, we construct CTARG and STARG. CTARG(1) is */
/* just the target itself, and STARG(1,1) is just a zero */
/* vector, that is, the position of the target relative */
/* to itself. */
/* Then we follow the chain, filling up CTARG and STARG */
/* as we go. We use SPKSFS to search through loaded */
/* files to find the first segment applicable to CTARG(1) */
/* and time ET. Then we use SPKPVN to compute the position */
/* of the body CTARG(1) at ET in the segment that was found */
/* and get its center and frame of motion (CTARG(2) and TFRAME(2). */
/* We repeat the process for CTARG(2) and so on, until */
/* there is no data found for some CTARG(I) or until we */
/* reach the SSB. */
/* Next, we find centers and positions in a similar manner */
/* for the observer. It's a similar construction as */
/* described above, but I is always 1. COBS and SOBS */
/* are overwritten with each new center and position, */
/* beginning at OBS. However, we stop when we encounter */
/* a common center of motion, that is when COBS is equal */
/* to CTARG(I) for some I. */
/* Finally, we compute the desired position of the target */
/* relative to the observer by subtracting the position of */
/* the observing body relative to the common node from */
/* the position of the target body relative to the common */
/* node. */
/* CTPOS is the position in CTARG of the common node. */
/* Since the upgrade to use hashes and counter bypass ZZNAMFRM */
/* became more efficient in looking up frame IDs than IRFNUM. So the */
/* original order of calls "IRFNUM first, NAMFRM second" was */
/* switched to "ZZNAMFRM first, IRFNUM second". */
/* The call to IRFNUM, now redundant for built-in inertial frames, */
/* was preserved to for a sole reason -- to still support the */
/* ancient and barely documented ability for the users to associate */
/* a frame with the fixed name 'DEFAULT' with any CHGIRF inertial */
/* frame code via CHGIRF's entry point IRFDEF. */
/* Note that in the case of ZZNAMFRM's failure to resolve name and */
/* IRFNUM's success to do so, the code returned by IRFNUM for */
/* 'DEFAULT' frame is *not* copied to the saved code SVREFI (which */
/* would be set to 0 by ZZNAMFRM) to make sure that on subsequent */
/* calls ZZNAMFRM does not do a bypass (as SVREFI always forced look */
/* up) and calls IRFNUM again to reset the 'DEFAULT's frame ID */
/* should it change between the calls. */
zznamfrm_(svctr1, svref, &svrefi, ref, &refid, (ftnlen)32, ref_len);
if (refid == 0) {
irfnum_(ref, &refid, ref_len);
}
if (refid == 0) {
if (frstnp_(ref, ref_len) > 0) {
setmsg_("The string supplied to specify the reference frame, ('#"
"') contains non-printing characters. The two most commo"
"n causes for this kind of error are: 1. an error in the "
"call to SPKGPS; 2. an uninitialized variable. ", (ftnlen)
213);
errch_("#", ref, (ftnlen)1, ref_len);
} else if (s_cmp(ref, " ", ref_len, (ftnlen)1) == 0) {
setmsg_("The string supplied to specify the reference frame is b"
"lank. The most common cause for this kind of error is a"
"n uninitialized variable. ", (ftnlen)137);
} else {
setmsg_("The string supplied to specify the reference frame was "
"'#'. This frame is not recognized. Possible causes for "
"this error are: 1. failure to load the frame definition "
"into the kernel pool; 2. An out-of-date edition of the t"
"oolkit. ", (ftnlen)231);
errch_("#", ref, (ftnlen)1, ref_len);
}
sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
}
/* Fill in CTARG and STARG until no more data is found */
/* or until we reach the SSB. If the chain gets too */
/* long to fit in CTARG, that is if I equals CHLEN, */
/* then overwrite the last elements of CTARG and STARG. */
/* Note the check for FAILED in the loop. If SPKSFS */
/* or SPKPVN happens to fail during execution, and the */
/* current error handling action is to NOT abort, then */
/* FOUND may be stuck at TRUE, CTARG(I) will never */
/* become zero, and the loop will execute indefinitely. */
/* Construct CTARG and STARG. Begin by assigning the */
/* first elements: TARG and the position of TARG relative */
/* to itself. */
i__ = 1;
ctarg[(i__1 = i__ - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge("ctarg", i__1,
"spkgps_", (ftnlen)603)] = *targ;
found = TRUE_;
cleard_(&c__6, &starg[(i__1 = i__ * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "spkgps_", (ftnlen)606)]);
while(found && i__ < 20 && ctarg[(i__1 = i__ - 1) < 20 && 0 <= i__1 ?
i__1 : s_rnge("ctarg", i__1, "spkgps_", (ftnlen)608)] != *obs &&
ctarg[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 : s_rnge("ctarg",
i__2, "spkgps_", (ftnlen)608)] != 0) {
/* Find a file and segment that has position */
/* data for CTARG(I). */
spksfs_(&ctarg[(i__1 = i__ - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"ctarg", i__1, "spkgps_", (ftnlen)617)], et, &handle, descr,
ident, &found, (ftnlen)40);
if (found) {
/* Get the position of CTARG(I) relative to some */
/* center of motion. This new center goes in */
/* CTARG(I+1) and the position is called STEMP. */
++i__;
spkpvn_(&handle, descr, et, &tframe[(i__1 = i__ - 1) < 20 && 0 <=
i__1 ? i__1 : s_rnge("tframe", i__1, "spkgps_", (ftnlen)
627)], &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ?
i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)627)], &
ctarg[(i__3 = i__ - 1) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"ctarg", i__3, "spkgps_", (ftnlen)627)]);
/* Here's what we have. STARG is the position of CTARG(I-1) */
/* relative to CTARG(I) in reference frame TFRAME(I) */
/* If one of the routines above failed during */
/* execution, we just give up and check out. */
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
}
}
tframe[0] = tframe[1];
/* If the loop above ended because we ran out of */
/* room in the arrays CTARG and STARG, then we */
/* continue finding positions but we overwrite the */
/* last elements of CTARG and STARG. */
/* If, as a result, the first common node is */
/* overwritten, we'll just have to settle for */
/* the last common node. This will cause a small */
/* loss of precision, but it's better than other */
/* alternatives. */
if (i__ == 20) {
while(found && ctarg[19] != 0 && ctarg[19] != *obs) {
/* Find a file and segment that has position */
/* data for CTARG(CHLEN). */
spksfs_(&ctarg[19], et, &handle, descr, ident, &found, (ftnlen)40)
;
if (found) {
/* Get the position of CTARG(CHLEN) relative to */
/* some center of motion. The new center */
/* overwrites the old. The position is called */
/* STEMP. */
spkpvn_(&handle, descr, et, &tmpfrm, stemp, &ctarg[19]);
/* Add STEMP to the position of TARG relative to */
/* the old center to get the position of TARG */
/* relative to the new center. Overwrite */
/* the last element of STARG. */
if (tframe[19] == tmpfrm) {
moved_(&starg[114], &c__3, vtemp);
} else if (tmpfrm > 0 && tmpfrm <= 21 && tframe[19] > 0 &&
tframe[19] <= 21) {
irfrot_(&tframe[19], &tmpfrm, rot);
mxv_(rot, &starg[114], vtemp);
} else {
refchg_(&tframe[19], &tmpfrm, et, psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, &starg[114], vtemp);
}
vadd_(vtemp, stemp, &starg[114]);
tframe[19] = tmpfrm;
/* If one of the routines above failed during */
/* execution, we just give up and check out. */
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
}
}
}
nct = i__;
/* NCT is the number of elements in CTARG, */
/* the chain length. We have in hand the following information */
/* STARG(1...3,K) position of body */
/* CTARG(K-1) relative to body CTARG(K) in the frame */
/* TFRAME(K) */
/* For K = 2,..., NCT. */
/* CTARG(1) = TARG */
/* STARG(1...3,1) = ( 0, 0, 0 ) */
/* TFRAME(1) = TFRAME(2) */
/* Now follow the observer's chain. Assign */
/* the first values for COBS and SOBS. */
cobs = *obs;
cleard_(&c__6, sobs);
/* Perhaps we have a common node already. */
/* If so it will be the last node on the */
/* list CTARG. */
/* We let CTPOS will be the position of the common */
/* node in CTARG if one is found. It will */
/* be zero if COBS is not found in CTARG. */
if (ctarg[(i__1 = nct - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge("ctarg",
i__1, "spkgps_", (ftnlen)762)] == cobs) {
ctpos = nct;
cframe = tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "spkgps_", (ftnlen)764)];
} else {
ctpos = 0;
}
/* Repeat the same loop as above, but each time */
/* we encounter a new center of motion, check to */
/* see if it is a common node. (When CTPOS is */
/* not zero, CTARG(CTPOS) is the first common node.) */
/* Note that we don't need a centers array nor a */
/* positions array, just a single center and position */
/* is sufficient --- we just keep overwriting them. */
/* When the common node is found, we have everything */
/* we need in that one center (COBS) and position */
/* (SOBS-position of the target relative to COBS). */
found = TRUE_;
nofrm = TRUE_;
legs = 0;
while(found && cobs != 0 && ctpos == 0) {
/* Find a file and segment that has position */
/* data for COBS. */
spksfs_(&cobs, et, &handle, descr, ident, &found, (ftnlen)40);
if (found) {
/* Get the position of COBS; call it STEMP. */
/* The center of motion of COBS becomes the */
/* new COBS. */
if (legs == 0) {
spkpvn_(&handle, descr, et, &tmpfrm, sobs, &cobs);
} else {
spkpvn_(&handle, descr, et, &tmpfrm, stemp, &cobs);
}
if (nofrm) {
nofrm = FALSE_;
cframe = tmpfrm;
}
/* Add STEMP to the position of OBS relative to */
/* the old COBS to get the position of OBS */
/* relative to the new COBS. */
if (cframe == tmpfrm) {
/* On the first leg of the position of the observer, we */
/* don't have to add anything, the position of the */
/* observer is already in SOBS. We only have to add when */
/* the number of legs in the observer position is one or */
/* greater. */
if (legs > 0) {
vadd_(sobs, stemp, vtemp);
vequ_(vtemp, sobs);
}
} else if (tmpfrm > 0 && tmpfrm <= 21 && cframe > 0 && cframe <=
21) {
irfrot_(&cframe, &tmpfrm, rot);
mxv_(rot, sobs, vtemp);
vadd_(vtemp, stemp, sobs);
cframe = tmpfrm;
} else {
refchg_(&cframe, &tmpfrm, et, psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, sobs, vtemp);
vadd_(vtemp, stemp, sobs);
cframe = tmpfrm;
}
/* Check failed. We don't want to loop */
/* indefinitely. */
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
/* We now have one more leg of the path for OBS. Set */
/* LEGS to reflect this. Then see if the new center */
/* is a common node. If not, repeat the loop. */
++legs;
ctpos = isrchi_(&cobs, &nct, ctarg);
}
}
/* If CTPOS is zero at this point, it means we */
/* have not found a common node though we have */
/* searched through all the available data. */
if (ctpos == 0) {
bodc2n_(targ, tname, &found, (ftnlen)40);
if (found) {
prefix_("# (", &c__0, tname, (ftnlen)3, (ftnlen)40);
suffix_(")", &c__0, tname, (ftnlen)1, (ftnlen)40);
repmi_(tname, "#", targ, tname, (ftnlen)40, (ftnlen)1, (ftnlen)40)
;
} else {
intstr_(targ, tname, (ftnlen)40);
}
bodc2n_(obs, oname, &found, (ftnlen)40);
if (found) {
prefix_("# (", &c__0, oname, (ftnlen)3, (ftnlen)40);
suffix_(")", &c__0, oname, (ftnlen)1, (ftnlen)40);
repmi_(oname, "#", obs, oname, (ftnlen)40, (ftnlen)1, (ftnlen)40);
} else {
intstr_(obs, oname, (ftnlen)40);
}
setmsg_("Insufficient ephemeris data has been loaded to compute the "
"position of TARG relative to OBS at the ephemeris epoch #. ",
(ftnlen)118);
etcal_(et, tstring, (ftnlen)80);
errch_("TARG", tname, (ftnlen)4, (ftnlen)40);
errch_("OBS", oname, (ftnlen)3, (ftnlen)40);
errch_("#", tstring, (ftnlen)1, (ftnlen)80);
sigerr_("SPICE(SPKINSUFFDATA)", (ftnlen)20);
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
/* If CTPOS is not zero, then we have reached a */
/* common node, specifically, */
/* CTARG(CTPOS) = COBS = CENTER */
/* (in diagram below). The POSITION of the target */
/* (TARG) relative to the observer (OBS) is just */
/* STARG(1,CTPOS) - SOBS. */
/* SOBS */
/* CENTER ---------------->OBS */
/* | . */
/* | . N */
/* S | . O */
/* T | . I */
/* A | . T */
/* R | . I */
/* G | . S */
/* | . O */
/* | . P */
/* V L */
/* TARG */
/* And the light-time between them is just */
/* | POSITION | */
/* LT = --------- */
/* c */
/* Compute the position of the target relative to CTARG(CTPOS) */
if (ctpos == 1) {
tframe[0] = cframe;
}
i__1 = ctpos - 1;
for (i__ = 2; i__ <= i__1; ++i__) {
if (tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 : s_rnge("tframe"
, i__2, "spkgps_", (ftnlen)960)] == tframe[(i__3 = i__) < 20
&& 0 <= i__3 ? i__3 : s_rnge("tframe", i__3, "spkgps_", (
ftnlen)960)]) {
vadd_(&starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ? i__2 :
s_rnge("starg", i__2, "spkgps_", (ftnlen)962)], &starg[(
i__3 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__3 ? i__3 :
s_rnge("starg", i__3, "spkgps_", (ftnlen)962)], stemp);
moved_(stemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)
963)]);
} else if (tframe[(i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"tframe", i__3, "spkgps_", (ftnlen)965)] > 0 && tframe[(i__3 =
i__) < 20 && 0 <= i__3 ? i__3 : s_rnge("tframe", i__3, "spk"
"gps_", (ftnlen)965)] <= 21 && tframe[(i__2 = i__ - 1) < 20 &&
0 <= i__2 ? i__2 : s_rnge("tframe", i__2, "spkgps_", (ftnlen)
965)] > 0 && tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2
: s_rnge("tframe", i__2, "spkgps_", (ftnlen)965)] <= 21) {
irfrot_(&tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 :
s_rnge("tframe", i__2, "spkgps_", (ftnlen)967)], &tframe[(
i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge("tframe",
i__3, "spkgps_", (ftnlen)967)], rot);
mxv_(rot, &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ? i__2 :
s_rnge("starg", i__2, "spkgps_", (ftnlen)968)], stemp);
vadd_(stemp, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__2
? i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)969)],
vtemp);
moved_(vtemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)
970)]);
} else {
refchg_(&tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 :
s_rnge("tframe", i__2, "spkgps_", (ftnlen)974)], &tframe[(
i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge("tframe",
i__3, "spkgps_", (ftnlen)974)], et, psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ?
i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)981)],
stemp);
vadd_(stemp, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__2
? i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)982)],
vtemp);
moved_(vtemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "spkgps_", (ftnlen)
983)]);
}
}
/* To avoid unnecessary frame transformations we'll do */
/* a bit of extra decision making here. It's a lot */
/* faster to make logical checks than it is to compute */
/* frame transformations. */
if (tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge("tframe",
i__1, "spkgps_", (ftnlen)996)] == cframe) {
vsub_(&starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "spkgps_", (ftnlen)998)], sobs, pos);
} else if (tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "spkgps_", (ftnlen)1000)] == refid) {
/* If the last frame associated with the target is already */
/* in the requested output frame, we convert the position of */
/* the observer to that frame and then subtract the position */
/* of the observer from the position of the target. */
if (refid > 0 && refid <= 21 && cframe > 0 && cframe <= 21) {
irfrot_(&cframe, &refid, rot);
mxv_(rot, sobs, stemp);
} else {
refchg_(&cframe, &refid, et, psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, sobs, stemp);
}
/* We've now transformed SOBS into the requested reference frame. */
/* Set CFRAME to reflect this. */
cframe = refid;
vsub_(&starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "spkgps_", (ftnlen)1031)], stemp, pos);
} else if (cframe > 0 && cframe <= 21 && tframe[(i__1 = ctpos - 1) < 20 &&
0 <= i__1 ? i__1 : s_rnge("tframe", i__1, "spkgps_", (ftnlen)
1034)] > 0 && tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 :
s_rnge("tframe", i__1, "spkgps_", (ftnlen)1034)] <= 21) {
/* If both frames are inertial we use IRFROT instead of */
/* REFCHG to get things into a common frame. */
irfrot_(&tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "spkgps_", (ftnlen)1040)], &cframe, rot);
mxv_(rot, &starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "spkgps_", (ftnlen)1041)], stemp);
vsub_(stemp, sobs, pos);
} else {
/* Use the more general routine REFCHG to make the transformation. */
refchg_(&tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "spkgps_", (ftnlen)1048)], &cframe, et,
psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, &starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "spkgps_", (ftnlen)1055)], stemp);
vsub_(stemp, sobs, pos);
}
/* Finally, rotate as needed into the requested frame. */
if (cframe == refid) {
/* We don't have to do anything in this case. */
} else if (refid > 0 && refid <= 21 && cframe > 0 && cframe <= 21) {
/* Since both frames are inertial, we use the more direct */
/* routine IRFROT to get the transformation to REFID. */
irfrot_(&cframe, &refid, rot);
mxv_(rot, pos, stemp);
moved_(stemp, &c__3, pos);
} else {
refchg_(&cframe, &refid, et, psxfrm);
if (failed_()) {
chkout_("SPKGPS", (ftnlen)6);
return 0;
}
mxv_(psxfrm, pos, stemp);
moved_(stemp, &c__3, pos);
}
*lt = vnorm_(pos) / clight_();
chkout_("SPKGPS", (ftnlen)6);
return 0;
} /* spkgps_ */
/* $Procedure STELAB ( Stellar Aberration ) */
/* Subroutine */ int stelab_(doublereal *pobj, doublereal *vobs, doublereal *
appobj)
{
/* Builtin functions */
double asin(doublereal);
/* Local variables */
extern /* Subroutine */ int vhat_(doublereal *, doublereal *);
doublereal vbyc[3];
extern /* Subroutine */ int vscl_(doublereal *, doublereal *, doublereal *
);
extern doublereal vdot_(doublereal *, doublereal *);
doublereal h__[3], u[3];
extern /* Subroutine */ int chkin_(char *, ftnlen), moved_(doublereal *,
integer *, doublereal *), errdp_(char *, doublereal *, ftnlen),
vcrss_(doublereal *, doublereal *, doublereal *);
extern doublereal vnorm_(doublereal *);
extern /* Subroutine */ int vrotv_(doublereal *, doublereal *, doublereal
*, doublereal *);
extern doublereal clight_(void);
doublereal onebyc, sinphi;
extern /* Subroutine */ int sigerr_(char *, ftnlen), chkout_(char *,
ftnlen), setmsg_(char *, ftnlen);
doublereal lensqr;
extern logical return_(void);
doublereal phi;
/* $ Abstract */
/* Correct the apparent position of an object for stellar */
/* aberration. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* None. */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Brief_I/O */
/* VARIABLE I/O DESCRIPTION */
/* -------- --- -------------------------------------------------- */
/* POBJ I Position of an object with respect to the */
/* observer. */
/* VOBS I Velocity of the observer with respect to the */
/* Solar System barycenter. */
/* APPOBJ O Apparent position of the object with respect to */
/* the observer, corrected for stellar aberration. */
/* $ Detailed_Input */
/* POBJ is the position (x, y, z, km) of an object with */
/* respect to the observer, possibly corrected for */
/* light time. */
/* VOBS is the velocity (dx/dt, dy/dt, dz/dt, km/sec) */
/* of the observer with respect to the Solar System */
/* barycenter. */
/* $ Detailed_Output */
/* APPOBJ is the apparent position of the object relative */
/* to the observer, corrected for stellar aberration. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If the velocity of the observer is greater than or equal */
/* to the speed of light, the error SPICE(VALUEOUTOFRANGE) */
/* is signaled. */
/* $ Files */
/* None. */
/* $ Particulars */
/* Let r be the vector from the observer to the object, and v be */
/* - - */
/* the velocity of the observer with respect to the Solar System */
/* barycenter. Let w be the angle between them. The aberration */
/* angle phi is given by */
/* sin(phi) = v sin(w) / c */
/* Let h be the vector given by the cross product */
/* - */
/* h = r X v */
/* - - - */
/* Rotate r by phi radians about h to obtain the apparent position */
/* - - */
/* of the object. */
/* $ Examples */
/* In the following example, STELAB is used to correct the position */
/* of a target body for stellar aberration. */
/* (Previous subroutine calls have loaded the SPK file and */
/* the leapseconds kernel file.) */
/* C */
/* C Get the geometric state of the observer OBS relative to */
/* C the solar system barycenter. */
/* C */
/* CALL SPKSSB ( OBS, ET, 'J2000', SOBS ) */
/* C */
/* C Get the light-time corrected position TPOS of the target */
/* C body TARG as seen by the observer. Normally we would */
/* C call SPKPOS to obtain this vector, but we already have */
/* C the state of the observer relative to the solar system */
/* C barycenter, so we can avoid looking up that state twice */
/* C by calling SPKAPO. */
/* C */
/* CALL SPKAPO ( TARG, ET, 'J2000', SOBS, 'LT', TPOS, LT ) */
/* C */
/* C Apply the correction for stellar aberration to the */
/* C light-time corrected position of the target body. */
/* C The corrected position is returned in the argument */
/* C PCORR. */
/* C */
/* CALL STELAB ( TPOS, SOBS(4), PCORR ) */
/* Note that this example is somewhat contrived. The sequence */
/* of calls above could be replaced by a single call to SPKEZP, */
/* using the aberration correction flag 'LT+S'. */
/* For more information on aberration-corrected states or */
/* positions, see the headers of any of the routines */
/* SPKEZR */
/* SPKEZ */
/* SPKPOS */
/* SPKEZP */
/* $ Restrictions */
/* None. */
/* $ Literature_References */
/* 1) W.M. Owen, Jr., JPL IOM #314.8-524, "The Treatment of */
/* Aberration in Optical Navigation", 8 February 1985. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* H.A. Neilan (JPL) */
/* W.L. Taber (JPL) */
/* I.M. Underwood (JPL) */
/* $ Version */
/* - SPICELIB Version 1.1.1, 8-JAN-2008 (NJB) */
/* The header example was updated to remove references */
/* to SPKAPP. */
/* - SPICELIB Version 1.1.0, 8-FEB-1999 (WLT) */
/* The example was corrected so that SOBS(4) is passed */
/* into STELAB instead of STARG(4). */
/* - SPICELIB Version 1.0.2, 10-MAR-1992 (WLT) */
/* Comment section for permuted index source lines was added */
/* following the header. */
/* - SPICELIB Version 1.0.1, 8-AUG-1990 (HAN) */
/* Examples section of the header was updated to replace */
/* calls to the GEF ephemeris readers by calls to the */
/* new SPK ephemeris reader. */
/* - SPICELIB Version 1.0.0, 31-JAN-1990 (IMU) (WLT) */
/* -& */
/* $ Index_Entries */
/* stellar aberration */
/* -& */
/* $ Revisions */
/* - Beta Version 2.1.0, 9-MAR-1989 (HAN) */
/* Declaration of the variable LIGHT was removed from the code. */
/* The variable was declared but never used. */
/* - Beta Version 2.0.0, 28-DEC-1988 (HAN) */
/* Error handling was added to check the velocity of the */
/* observer. If the velocity of the observer is greater */
/* than or equal to the speed of light, the error */
/* SPICE(VALUEOUTOFRANGE) is signalled. */
/* -& */
/* SPICELIB functions */
/* Local variables */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("STELAB", (ftnlen)6);
}
/* We are not going to compute the aberrated vector in exactly the */
/* way described in the particulars section. We can combine some */
/* steps and we take some precautions to prevent floating point */
/* overflows. */
/* Get a unit vector that points in the direction of the object */
/* ( u_obj ). */
vhat_(pobj, u);
/* Get the velocity vector scaled with respect to the speed of light */
/* ( v/c ). */
onebyc = 1. / clight_();
vscl_(&onebyc, vobs, vbyc);
/* If the square of the length of the velocity vector is greater than */
/* or equal to one, the speed of the observer is greater than or */
/* equal to the speed of light. The observer speed is definitely out */
/* of range. Signal an error and check out. */
lensqr = vdot_(vbyc, vbyc);
if (lensqr >= 1.) {
setmsg_("Velocity components of observer were: dx/dt = *, dy/dt = *"
", dz/dt = *.", (ftnlen)71);
errdp_("*", vobs, (ftnlen)1);
errdp_("*", &vobs[1], (ftnlen)1);
errdp_("*", &vobs[2], (ftnlen)1);
sigerr_("SPICE(VALUEOUTOFRANGE)", (ftnlen)22);
chkout_("STELAB", (ftnlen)6);
return 0;
}
/* Compute u_obj x (v/c) */
vcrss_(u, vbyc, h__);
/* If the magnitude of the vector H is zero, the observer is moving */
/* along the line of sight to the object, and no correction is */
/* required. Otherwise, rotate the position of the object by phi */
/* radians about H to obtain the apparent position. */
sinphi = vnorm_(h__);
if (sinphi != 0.) {
phi = asin(sinphi);
vrotv_(pobj, h__, &phi, appobj);
} else {
moved_(pobj, &c__3, appobj);
}
chkout_("STELAB", (ftnlen)6);
return 0;
} /* stelab_ */
/* $Procedure LTIME ( Light Time ) */
/* Subroutine */ int ltime_(doublereal *etobs, integer *obs, char *dir,
integer *targ, doublereal *ettarg, doublereal *elapsd, ftnlen dir_len)
{
/* Builtin functions */
integer s_cmp(char *, char *, ftnlen, ftnlen);
/* Local variables */
doublereal sobs[6], myet, c__;
integer r__;
extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
ftnlen, ftnlen);
doublereal starg[6];
extern doublereal vdist_(doublereal *, doublereal *);
extern integer rtrim_(char *, ftnlen);
extern logical failed_(void);
doublereal lt;
extern doublereal clight_(void);
integer bcentr;
extern /* Subroutine */ int spkgeo_(integer *, doublereal *, char *,
integer *, doublereal *, doublereal *, ftnlen), sigerr_(char *,
ftnlen), chkout_(char *, ftnlen), setmsg_(char *, ftnlen);
extern logical return_(void);
/* $ Abstract */
/* This routine computes the transmit (or receive) time */
/* of a signal at a specified target, given the receive */
/* (or transmit) time at a specified observer. The elapsed */
/* time between transmit and receive is also returned. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* None. */
/* $ Keywords */
/* SPK */
/* $ Declarations */
/* $ Brief_I/O */
/* VARIABLE I/O DESCRIPTION */
/* -------- --- -------------------------------------------------- */
/* ETOBS I Epoch of a signal at some observer */
/* OBS I NAIF-id of some observer */
/* DIR I Direction the signal travels ( '->' or '<-' ) */
/* TARG I NAIF-id of the target object */
/* ETTARG O Epoch of the signal at the target */
/* ELAPSD O Time between transmit and receipt of the signal */
/* $ Detailed_Input */
/* ETOBS is an epoch expressed in ephemeris second (TDB) */
/* past the epoch of the J2000 reference system. */
/* This is the time at which an electromagnetic */
/* signal is "at" the observer. */
/* OBS is the NAIF-id of some observer. */
/* DIR is the direction the signal travels. The */
/* acceptable values are '->' and '<-'. When */
/* you read the calling sequence from left to */
/* right, the "arrow" given by DIR indicates */
/* which way the electromagnetic signal is travelling. */
/* If the argument list reads as below, */
/* ..., OBS, '->', TARG, ... */
/* the signal is travelling from the observer to the */
/* target. */
/* If the argument reads as */
/* ..., OBS, '<-', TARG */
/* the signal is travelling from the target to */
/* the observer. */
/* TARG is the NAIF-id of the target. */
/* $ Detailed_Output */
/* ETTARG is the epoch expressed in ephemeris seconds (TDB) */
/* past the epoch of the J2000 reference system */
/* at which the electromagnetic signal is "at" the */
/* target body. */
/* Note ETTARG is computed using only Newtonian */
/* assumptions about the propagation of light. */
/* ELAPSD is the number of ephemeris seconds (TDB) between */
/* transmission and receipt of the signal. */
/* ELAPSD = DABS( ETOBS - ETTARG ) */
/* $ Parameters */
/* None. */
/* $ Files */
/* None. */
/* $ Exceptions */
/* 1) If DIR is not one of '->' or '<-' the error */
/* 'SPICE(BADDIRECTION)' will be signalled. In this case */
/* ETTARG and ELAPSD will not be altered from their */
/* input values. */
/* 2) If insufficient ephemeris information is available to */
/* compute the outputs ETTARG and ELAPSD, or if observer */
/* or target is not recognized, the problems is diagnosed */
/* by a routine in the call tree of this routine. */
/* In this case, the value of ETTARG will be set to ETOBS */
/* and ELAPSD will be set to zero. */
/* $ Particulars */
/* Suppose a radio signal travels between two solar system */
/* objects. Given an ephemeris for the two objects, which way */
/* the signal is travelling, and the time when the signal is */
/* "at" at one of the objects (the observer OBS), this routine */
/* determines when the signal is "at" the other object (the */
/* target TARG). It also returns the elapsed time between */
/* transmission and receipt of the signal. */
/* $ Examples */
/* Example 1. */
/* ---------- */
/* Suppose a signal is transmitted at time ET from the Goldstone */
/* tracking site (id-code 399001) to a spacecraft whose id-code */
/* is -77. */
/* signal travelling to spacecraft */
/* * -._.-._.-._.-._.-._.-._.-._.-._.-> * */
/* Goldstone (OBS=399001) Spacecraft (TARG = -77) */
/* at epoch ETOBS(given) at epoch ETTARG(unknown) */
/* Assuming that all of the required SPICE kernels have been */
/* loaded, the code fragment below shows how to compute the */
/* time (ARRIVE) at which the signal arrives at the spacecraft */
/* and how long (HOWLNG) it took the signal to reach the spacecraft. */
/* (Note that we display the arrival time as the number of seconds */
/* past J2000.) */
/* OBS = 399001 */
/* TARG = -77 */
/* ETOBS = ET */
/* CALL LTIME ( ETOBS, OBS, '->', TARG, ARRIVE, HOWLNG ) */
/* CALL ETCAL */
/* WRITE (*,*) 'The signal arrived at time: ', ARRIVE */
/* WRITE (*,*) 'It took ', HOWLNG, ' seconds to get there.' */
/* Example 2. */
/* ---------- */
/* Suppose a signal is received at the Goldstone tracking sight */
/* at epoch ET from the spacecraft of the previous example. */
/* signal sent from spacecraft */
/* * <-._.-._.-._.-._.-._.-._.-._.-._.- * */
/* Goldstone (OBS=399001) Spacecraft (TARG = -77) */
/* at epoch ETOBS(given) at epoch ETTARG(unknown) */
/* Again assuming that all the required kernels have been loaded */
/* the code fragment below computes the epoch at which the */
/* signal was transmitted from the spacecraft. */
/* OBS = 399001 */
/* TARG = -77 */
/* ETOBS = ET */
/* CALL LTIME ( ETOBS, OBS, '<-', TARG, SENT, HOWLNG ) */
/* CALL ETCAL */
/* WRITE (*,*) 'The signal was transmitted at: ', SENT */
/* WRITE (*,*) 'It took ', HOWLNG, ' seconds to get here.' */
/* EXAMPLE 3 */
/* --------- */
/* Suppose there is a transponder on board the spacecraft of */
/* the previous examples that transmits a signal back to the */
/* sender exactly 1 microsecond after a signal arrives at */
/* the spacecraft. If we send a signal from Goldstone */
/* to the spacecraft and wait to receive it at Canberra. */
/* What will be the epoch at which the return signal arrives */
/* in Canberra? ( The id-code for Canberra is 399002 ). */
/* Again, assuming we've loaded all the necessary kernels, */
/* the fragment below will give us the answer. */
/* GSTONE = 399001 */
/* SC = -77 */
/* CANBER = 399002 */
/* ETGOLD = ET */
/* CALL LTIME ( ETGOLD, GSTONE, '->', SC, SCGET, LT1 ) */
/* Account for the microsecond delay between receipt and transmit */
/* SCSEND = SCGET + 0.000001 */
/* CALL LTIME ( SCSEND, SC, '->', CANBER, ETCANB, LT2 ) */
/* RNDTRP = ETCANB - ETGOLD */
/* WRITE (*,*) 'The signal arrives in Canberra at: ', ETCANB */
/* WRITE (*,*) 'Round trip time for the signal was: ', RNDTRP */
/* $ Restrictions */
/* None. */
/* $ Author_and_Institution */
/* W.L. Taber (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.1.2, 22-SEP-2004 (EDW) */
/* Placed Copyright after Abstract. */
/* - SPICELIB Version 1.1.1, 18-NOV-1996 (WLT) */
/* Errors in the examples section were corrected. */
/* - SPICELIB Version 1.1.0, 10-JUL-1996 (WLT) */
/* Added Copyright Notice to the header. */
/* - SPICELIB Version 1.0.0, 10-NOV-1995 (WLT) */
/* -& */
/* $ Index_Entries */
/* Compute uplink and downlink light time */
/* -& */
/* SPICELIB Functions */
/* Local Variables */
if (return_()) {
return 0;
}
chkin_("LTIME", (ftnlen)5);
/* First perform the obvious error check. */
if (s_cmp(dir, "->", (ftnlen)2, (ftnlen)2) != 0 && s_cmp(dir, "<-", (
ftnlen)2, (ftnlen)2) != 0) {
setmsg_("The direction specifier for the signal was '#' it must be "
"either '->' or '<-'. ", (ftnlen)80);
r__ = rtrim_(dir, (ftnlen)2);
errch_("#", dir, (ftnlen)1, r__);
sigerr_("SPICE(BADDIRECTION)", (ftnlen)19);
chkout_("LTIME", (ftnlen)5);
return 0;
}
/* We need two constants, the speed of light and the id-code */
/* for the solar system barycenter. */
c__ = clight_();
bcentr = 0;
myet = *etobs;
/* First get the barycenter relative states of the observer */
/* and target. */
spkgeo_(obs, &myet, "J2000", &bcentr, sobs, <, (ftnlen)5);
spkgeo_(targ, &myet, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
/* The rest is straight forward. We either add the elapsed */
/* time to get the next state or subtract the elapsed time. */
/* This depends on whether we are receiving or transmitting */
/* at the observer. */
/* Note that 3 iterations as performed here gives us */
/* Newtonian accuracy to the nanosecond level for all */
/* known objects in the solar system. The ephemeris */
/* is certain to be much worse than this. */
if (s_cmp(dir, "->", (ftnlen)2, (ftnlen)2) == 0) {
*ettarg = myet + *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet + *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet + *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet + *elapsd;
} else {
*ettarg = myet - *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet - *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet - *elapsd;
spkgeo_(targ, ettarg, "J2000", &bcentr, starg, <, (ftnlen)5);
*elapsd = vdist_(sobs, starg) / c__;
*ettarg = myet - *elapsd;
}
if (failed_()) {
*ettarg = myet;
*elapsd = 0.;
}
chkout_("LTIME", (ftnlen)5);
return 0;
} /* ltime_ */
/* $Procedure ZZSPKFLT ( SPK function, light time and rate ) */
/* Subroutine */ int zzspkflt_(S_fp trgsub, doublereal *et, char *ref, char *
abcorr, doublereal *stobs, doublereal *starg, doublereal *lt,
doublereal *dlt, ftnlen ref_len, ftnlen abcorr_len)
{
/* Initialized data */
static logical pass1 = TRUE_;
static char prvcor[5] = " ";
/* System generated locals */
doublereal d__1, d__2, d__3, d__4;
/* Builtin functions */
integer s_cmp(char *, char *, ftnlen, ftnlen);
/* Subroutine */ int s_copy(char *, char *, ftnlen, ftnlen);
/* Local variables */
doublereal dist;
extern doublereal vdot_(doublereal *, doublereal *);
static logical xmit;
extern /* Subroutine */ int zzvalcor_(char *, logical *, ftnlen);
doublereal a, b, c__;
integer i__;
extern /* Subroutine */ int vaddg_(doublereal *, doublereal *, integer *,
doublereal *);
integer refid;
extern /* Subroutine */ int chkin_(char *, ftnlen);
doublereal epoch;
extern /* Subroutine */ int errch_(char *, char *, ftnlen, ftnlen);
static logical usecn;
extern /* Subroutine */ int vlcom_(doublereal *, doublereal *, doublereal
*, doublereal *, doublereal *), vsubg_(doublereal *, doublereal *,
integer *, doublereal *);
doublereal lterr;
static logical uselt;
extern doublereal vnorm_(doublereal *);
doublereal prvlt;
extern logical failed_(void);
extern doublereal clight_(void);
logical attblk[15];
extern doublereal touchd_(doublereal *);
extern /* Subroutine */ int sigerr_(char *, ftnlen), chkout_(char *,
ftnlen);
doublereal ctrssb[6];
integer ltsign;
extern /* Subroutine */ int irfnum_(char *, integer *, ftnlen), setmsg_(
char *, ftnlen);
doublereal ssbtrg[6];
integer trgctr;
extern /* Subroutine */ int spkssb_(integer *, doublereal *, char *,
doublereal *, ftnlen);
integer numitr;
extern logical return_(void);
logical usestl;
doublereal sttctr[6];
/* $ Abstract */
/* SPICE Private routine intended solely for the support of SPICE */
/* routines. Users should not call this routine directly due */
/* to the volatile nature of this routine. */
/* Return the state (position and velocity) of a target body */
/* relative to an observer, optionally corrected for light time, */
/* expressed relative to an inertial reference frame. An input */
/* subroutine provides the state of the target relative to its */
/* center of motion. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* SPK */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Abstract */
/* Include file zzabcorr.inc */
/* SPICE private file intended solely for the support of SPICE */
/* routines. Users should not include this file directly due */
/* to the volatile nature of this file */
/* The parameters below define the structure of an aberration */
/* correction attribute block. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Parameters */
/* An aberration correction attribute block is an array of logical */
/* flags indicating the attributes of the aberration correction */
/* specified by an aberration correction string. The attributes */
/* are: */
/* - Is the correction "geometric"? */
/* - Is light time correction indicated? */
/* - Is stellar aberration correction indicated? */
/* - Is the light time correction of the "converged */
/* Newtonian" variety? */
/* - Is the correction for the transmission case? */
/* - Is the correction relativistic? */
/* The parameters defining the structure of the block are as */
/* follows: */
/* NABCOR Number of aberration correction choices. */
/* ABATSZ Number of elements in the aberration correction */
/* block. */
/* GEOIDX Index in block of geometric correction flag. */
/* LTIDX Index of light time flag. */
/* STLIDX Index of stellar aberration flag. */
/* CNVIDX Index of converged Newtonian flag. */
/* XMTIDX Index of transmission flag. */
/* RELIDX Index of relativistic flag. */
/* The following parameter is not required to define the block */
/* structure, but it is convenient to include it here: */
/* CORLEN The maximum string length required by any aberration */
/* correction string */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 18-DEC-2004 (NJB) */
/* -& */
/* Number of aberration correction choices: */
/* Aberration correction attribute block size */
/* (number of aberration correction attributes): */
/* Indices of attributes within an aberration correction */
/* attribute block: */
/* Maximum length of an aberration correction string: */
/* End of include file zzabcorr.inc */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* TRGSUB I Target body state subroutine. */
/* ET I Observer epoch. */
/* REF I Inertial reference frame of output state. */
/* ABCORR I Aberration correction flag. */
/* STOBS I State of the observer relative to the SSB. */
/* STARG O State of target. */
/* LT O One way light time between observer and target. */
/* DLT O Derivative of light time with respect to time. */
/* $ Detailed_Input */
/* TRGSUB is the name of an external subroutine that returns */
/* the geometric state of the target body relative to a */
/* center of motion, expressed in the inertial reference */
/* frame REF, at the epoch ET. */
/* The calling sequence of TRGSUB is */
/* SUBROUTINE TRGSUB ( ET, REF, TRGCTR, STATE ) */
/* DOUBLE PRECISION ET */
/* CHARACTER*(*) REF */
/* INTEGER TRGCTR */
/* DOUBLE PRECISION STATE ( 6 ) */
/* The inputs of TRGSUB are ET and REF; the outputs */
/* are TRGCTR and STATE. STATE is the geometric state */
/* of the target relative to the returned center of */
/* motion at ET, expressed in the frame REF. */
/* The target and observer define a state vector whose */
/* position component points from the observer to the */
/* target. */
/* ET is the ephemeris time, expressed as seconds past */
/* J2000 TDB, at which the state of the target body */
/* relative to the observer is to be computed. ET */
/* refers to time at the observer's location. */
/* REF is the inertial reference frame with respect to which */
/* the input state STOBS and the output state STARG are */
/* expressed. REF must be recognized by the SPICE */
/* Toolkit. The acceptable frames are listed in the */
/* Frames Required Reading, as well as in the SPICELIB */
/* routine CHGIRF. */
/* Case and blanks are not significant in the string */
/* REF. */
/* ABCORR indicates the aberration corrections to be applied to */
/* the state of the target body to account for one-way */
/* light time. See the discussion in the Particulars */
/* section for recommendations on how to choose */
/* aberration corrections. */
/* If ABCORR includes the stellar aberration correction */
/* symbol '+S', this flag is simply ignored. Aside from */
/* the possible presence of this symbol, ABCORR may be */
/* any of the following: */
/* 'NONE' Apply no correction. Return the */
/* geometric state of the target body */
/* relative to the observer. */
/* The following values of ABCORR apply to the */
/* "reception" case in which photons depart from the */
/* target's location at the light-time corrected epoch */
/* ET-LT and *arrive* at the observer's location at ET: */
/* 'LT' Correct for one-way light time (also */
/* called "planetary aberration") using a */
/* Newtonian formulation. This correction */
/* yields the state of the target at the */
/* moment it emitted photons arriving at */
/* the observer at ET. */
/* The light time correction involves */
/* iterative solution of the light time */
/* equation. (See the Particulars section */
/* of SPKEZR for details.) The solution */
/* invoked by the 'LT' option uses one */
/* iteration. */
/* 'CN' Converged Newtonian light time */
/* correction. In solving the light time */
/* equation, the 'CN' correction iterates */
/* until the solution converges (three */
/* iterations on all supported platforms). */
/* Whether the 'CN+S' solution is */
/* substantially more accurate than the */
/* 'LT' solution depends on the geometry */
/* of the participating objects and on the */
/* accuracy of the input data. In all */
/* cases this routine will execute more */
/* slowly when a converged solution is */
/* computed. See the Particulars section of */
/* SPKEZR for a discussion of precision of */
/* light time corrections. */
/* The following values of ABCORR apply to the */
/* "transmission" case in which photons *depart* from */
/* the observer's location at ET and arrive at the */
/* target's location at the light-time corrected epoch */
/* ET+LT: */
/* 'XLT' "Transmission" case: correct for */
/* one-way light time using a Newtonian */
/* formulation. This correction yields the */
/* state of the target at the moment it */
/* receives photons emitted from the */
/* observer's location at ET. */
/* 'XCN' "Transmission" case: converged */
/* Newtonian light time correction. */
/* Neither special nor general relativistic effects are */
/* accounted for in the aberration corrections applied */
/* by this routine. */
/* Case and blanks are not significant in the string */
/* ABCORR. */
/* STOBS is the geometric (uncorrected) state of the observer */
/* relative to the solar system barycenter at epoch ET. */
/* STOBS is a 6-vector: the first three components of */
/* STOBS represent a Cartesian position vector; the last */
/* three components represent the corresponding velocity */
/* vector. STOBS is expressed relative to the inertial */
/* reference frame designated by REF. */
/* Units are always km and km/sec. */
/* $ Detailed_Output */
/* STARG is a Cartesian state vector representing the position */
/* and velocity of the target body relative to the */
/* specified observer. STARG is corrected for the */
/* specified aberration, and is expressed with respect */
/* to the specified inertial reference frame. The first */
/* three components of STARG represent the x-, y- and */
/* z-components of the target's position; last three */
/* components form the corresponding velocity vector. */
/* The position component of STARG points from the */
/* observer's location at ET to the aberration-corrected */
/* location of the target. Note that the sense of the */
/* position vector is independent of the direction of */
/* radiation travel implied by the aberration */
/* correction. */
/* Units are always km and km/sec. */
/* LT is the one-way light time between the observer and */
/* target in seconds. If the target state is corrected */
/* for light time, then LT is the one-way light time */
/* between the observer and the light time-corrected */
/* target location. */
/* DLT is the derivative with respect to barycentric */
/* dynamical time of the one way light time between */
/* target and observer: */
/* DLT = d(LT)/d(ET) */
/* DLT can also be described as the rate of change of */
/* one way light time. DLT is unitless, since LT and */
/* ET both have units of TDB seconds. */
/* If the observer and target are at the same position, */
/* then DLT is set to zero. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) For the convenience of the caller, the input aberration */
/* correction flag can call for stellar aberration correction via */
/* inclusion of the '+S' suffix. This portion of the aberration */
/* correction flag is ignored if present. */
/* 2) If ABCORR calls for stellar aberration but not light */
/* time corrections, the error SPICE(NOTSUPPORTED) is */
/* signaled. */
/* 3) If ABCORR calls for relativistic light time corrections, the */
/* error SPICE(NOTSUPPORTED) is signaled. */
/* 4) If the value of ABCORR is not recognized, the error */
/* is diagnosed by a routine in the call tree of this */
/* routine. */
/* 5) If the reference frame requested is not a recognized */
/* inertial reference frame, the error SPICE(UNKNOWNFRAME) */
/* is signaled. */
/* 6) If the state of the target relative to the solar system */
/* barycenter cannot be computed, the error will be diagnosed */
/* by routines in the call tree of this routine. */
/* 7) If the observer and target are at the same position, */
/* then DLT is set to zero. This situation could arise, */
/* for example, when the observer is Mars and the target */
/* is the Mars barycenter. */
/* 8) If a division by zero error would occur in the computation */
/* of DLT, the error SPICE(DIVIDEBYZERO) is signaled. */
/* $ Files */
/* This routine computes states using SPK files that have been */
/* loaded into the SPICE system, normally via the kernel loading */
/* interface routine FURNSH. Application programs typically load */
/* kernels once before this routine is called, for example during */
/* program initialization; kernels need not be loaded repeatedly. */
/* See the routine FURNSH and the SPK and KERNEL Required Reading */
/* for further information on loading (and unloading) kernels. */
/* If any of the ephemeris data used to compute STARG are expressed */
/* relative to a non-inertial frame in the SPK files providing those */
/* data, additional kernels may be needed to enable the reference */
/* frame transformations required to compute the state. Normally */
/* these additional kernels are PCK files or frame kernels. Any */
/* such kernels must already be loaded at the time this routine is */
/* called. */
/* $ Particulars */
/* This routine supports higher-level routines that can */
/* perform both light time and stellar aberration corrections */
/* and that use target states provided by subroutines rather */
/* than by the conventional, public SPK APIs. For example, this */
/* routine can be used for objects having fixed positions */
/* on the surfaces of planets. */
/* $ Examples */
/* See usage in ZZSPKFAP. */
/* $ Restrictions */
/* 1) This routine must not be called by routines of the SPICE */
/* frame subsystem. It must not be called by any portion of */
/* the SPK subsystem other than the private SPK function-based */
/* component. */
/* 2) The input subroutine TRGSUB must not call this routine. */
/* or any of the supporting, private SPK routines */
/* 3) When possible, the routine SPKGEO should be used instead of */
/* this routine to compute geometric states. SPKGEO introduces */
/* less round-off error when the observer and target have common */
/* center that is closer to both objects than is the solar */
/* system barycenter. */
/* 4) Unlike most other SPK state computation routines, this */
/* routine requires that the output state be relative to an */
/* inertial reference frame. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Version */
/* - SPICELIB Version 1.0.0, 04-JUL-2014 (NJB) */
/* Discussion of light time corrections was updated. Assertions */
/* that converged light time corrections are unlikely to be */
/* useful were removed. */
/* Last update was 22-FEB-2012 (NJB) */
/* -& */
/* $ Index_Entries */
/* low-level light time correction */
/* light-time corrected state from spk file */
/* get light-time corrected state */
/* -& */
/* $ Revisions */
/* None. */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* TOL is the tolerance used for a division-by-zero test */
/* performed prior to computation of DLT. */
/* Convergence limit: */
/* Maximum number of light time iterations for any */
/* aberration correction: */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
}
chkin_("ZZSPKFLT", (ftnlen)8);
if (pass1 || s_cmp(abcorr, prvcor, abcorr_len, (ftnlen)5) != 0) {
/* The aberration correction flag differs from the value it */
/* had on the previous call, if any. Analyze the new flag. */
zzvalcor_(abcorr, attblk, abcorr_len);
if (failed_()) {
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
/* The aberration correction flag is recognized; save it. */
s_copy(prvcor, abcorr, (ftnlen)5, abcorr_len);
/* Set logical flags indicating the attributes of the requested */
/* correction: */
/* XMIT is .TRUE. when the correction is for transmitted */
/* radiation. */
/* USELT is .TRUE. when any type of light time correction */
/* (normal or converged Newtonian) is specified. */
/* USECN indicates converged Newtonian light time correction. */
/* The above definitions are consistent with those used by */
/* ZZVALCOR. */
xmit = attblk[4];
uselt = attblk[1];
usecn = attblk[3];
usestl = attblk[2];
pass1 = FALSE_;
}
/* See if the reference frame is a recognized inertial frame. */
irfnum_(ref, &refid, ref_len);
if (refid == 0) {
setmsg_("The requested frame '#' is not a recognized inertial frame. "
, (ftnlen)60);
errch_("#", ref, (ftnlen)1, ref_len);
sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
/* Find the geometric state of the target body with respect to */
/* the solar system barycenter. Subtract the state of the */
/* observer to get the relative state. Use this to compute the */
/* one-way light time. */
(*trgsub)(et, ref, &trgctr, sttctr, ref_len);
spkssb_(&trgctr, et, ref, ctrssb, ref_len);
if (failed_()) {
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
vaddg_(ctrssb, sttctr, &c__6, ssbtrg);
vsubg_(ssbtrg, stobs, &c__6, starg);
dist = vnorm_(starg);
*lt = dist / clight_();
if (*lt == 0.) {
/* This can happen only if the observer and target are at the */
/* same position. We don't consider this an error, but we're not */
/* going to compute the light time derivative. */
*dlt = 0.;
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
if (! uselt) {
/* This is a special case: we're not using light time */
/* corrections, so the derivative */
/* of light time is just */
/* (1/c) * d(VNORM(STARG))/dt */
*dlt = vdot_(starg, &starg[3]) / (dist * clight_());
/* LT and DLT are both set, so we can return. */
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
/* To correct for light time, find the state of the target body */
/* at the current epoch minus the one-way light time. Note that */
/* the observer remains where it is. */
/* Determine the sign of the light time offset. */
if (xmit) {
ltsign = 1;
} else {
ltsign = -1;
}
/* Let NUMITR be the number of iterations we'll perform to */
/* compute the light time. */
if (usecn) {
numitr = 5;
} else {
numitr = 1;
}
i__ = 0;
lterr = 1.;
while(i__ < numitr && lterr > 1e-17) {
/* LT was set either prior to this loop or */
/* during the previous loop iteration. */
d__1 = *et + ltsign * *lt;
epoch = touchd_(&d__1);
(*trgsub)(&epoch, ref, &trgctr, sttctr, ref_len);
spkssb_(&trgctr, &epoch, ref, ctrssb, ref_len);
if (failed_()) {
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
vaddg_(ctrssb, sttctr, &c__6, ssbtrg);
vsubg_(ssbtrg, stobs, &c__6, starg);
prvlt = *lt;
d__1 = vnorm_(starg) / clight_();
*lt = touchd_(&d__1);
/* LTERR is the magnitude of the change between the current */
/* estimate of light time and the previous estimate, relative to */
/* the previous light time corrected epoch. */
/* Computing MAX */
d__3 = 1., d__4 = abs(epoch);
d__2 = (d__1 = *lt - prvlt, abs(d__1)) / max(d__3,d__4);
lterr = touchd_(&d__2);
++i__;
}
/* At this point, STARG contains the light time corrected */
/* state of the target relative to the observer. */
/* Compute the derivative of light time with respect */
/* to time: dLT/dt. Below we derive the formula for */
/* this quantity for the reception case. Let */
/* POBS be the position of the observer relative to the */
/* solar system barycenter. */
/* VOBS be the velocity of the observer relative to the */
/* solar system barycenter. */
/* PTARG be the position of the target relative to the */
/* solar system barycenter. */
/* VTARG be the velocity of the target relative to the */
/* solar system barycenter. */
/* S be the sign of the light time correction. S is */
/* negative for the reception case. */
/* The light-time corrected position of the target relative to */
/* the observer at observation time ET, given the one-way */
/* light time LT is: */
/* PTARG(ET+S*LT) - POBS(ET) */
/* The light-time corrected velocity of the target relative to */
/* the observer at observation time ET is */
/* VTARG(ET+S*LT)*( 1 + S*d(LT)/d(ET) ) - VOBS(ET) */
/* We need to compute dLT/dt. Below, we use the facts that, */
/* for a time-dependent vector X(t), */
/* ||X|| = <X,X> ** (1/2) */
/* d(||X||)/dt = (1/2)<X,X>**(-1/2) * 2 * <X,dX/dt> */
/* = <X,X>**(-1/2) * <X,dX/dt> */
/* = <X,dX/dt> / ||X|| */
/* Newtonian light time equation: */
/* LT = (1/c) * || PTARG(ET+S*LT) - POBS(ET)|| */
/* Differentiate both sides: */
/* dLT/dt = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* * < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT)*(1+S*d(LT)/d(ET)) - VOBS(ET) > */
/* = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* * ( < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT) - VOBS(ET) > */
/* + < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT) > * (S*d(LT)/d(ET)) ) */
/* Let */
/* A = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* B = < PTARG(ET+S*LT) - POBS(ET), VTARG(ET+S*LT) - VOBS(ET) > */
/* C = < PTARG(ET+S*LT) - POBS(ET), VTARG(ET+S*LT) > */
/* Then */
/* d(LT)/d(ET) = A * ( B + C * S*d(LT)/d(ET) ) */
/* which implies */
/* d(LT)/d(ET) = A*B / ( 1 - S*C*A ) */
a = 1. / (clight_() * vnorm_(starg));
b = vdot_(starg, &starg[3]);
c__ = vdot_(starg, &ssbtrg[3]);
/* For physically realistic target velocities, S*C*A cannot equal 1. */
/* We'll check for this case anyway. */
if (ltsign * c__ * a > .99999999989999999) {
setmsg_("Target range rate magnitude is approximately the speed of l"
"ight. The light time derivative cannot be computed.", (ftnlen)
110);
sigerr_("SPICE(DIVIDEBYZERO)", (ftnlen)19);
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
}
/* Compute DLT: the rate of change of light time. */
*dlt = a * b / (1. - ltsign * c__ * a);
/* Overwrite the velocity portion of the output state */
/* with the light-time corrected velocity. */
d__1 = ltsign * *dlt + 1.;
vlcom_(&d__1, &ssbtrg[3], &c_b19, &stobs[3], &starg[3]);
chkout_("ZZSPKFLT", (ftnlen)8);
return 0;
} /* zzspkflt_ */
/* $Procedure ZZGFSSOB ( GF, state of sub-observer point ) */
/* Subroutine */ int zzgfssob_(char *method, integer *trgid, doublereal *et,
char *fixref, char *abcorr, integer *obsid, doublereal *radii,
doublereal *state, ftnlen method_len, ftnlen fixref_len, ftnlen
abcorr_len)
{
/* Initialized data */
static logical first = TRUE_;
static integer prvobs = 0;
static integer prvtrg = 0;
static char svobs[36] = " ";
static char svtarg[36] = " ";
/* System generated locals */
integer i__1;
/* Builtin functions */
integer s_rnge(char *, integer, char *, integer);
/* Local variables */
doublereal dalt[2];
logical near__, geom;
extern /* Subroutine */ int vhat_(doublereal *, doublereal *), vscl_(
doublereal *, doublereal *, doublereal *);
extern doublereal vdot_(doublereal *, doublereal *);
logical xmit;
extern /* Subroutine */ int mxvg_(doublereal *, doublereal *, integer *,
integer *, doublereal *);
doublereal upos[3];
extern /* Subroutine */ int zzstelab_(logical *, doublereal *, doublereal
*, doublereal *, doublereal *, doublereal *), zzcorsxf_(logical *,
doublereal *, doublereal *, doublereal *);
integer i__;
extern /* Subroutine */ int zzprscor_(char *, logical *, ftnlen);
doublereal t;
extern /* Subroutine */ int vaddg_(doublereal *, doublereal *, integer *,
doublereal *);
doublereal scale;
extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
ftnlen, ftnlen);
doublereal savel[3];
logical found;
extern /* Subroutine */ int moved_(doublereal *, integer *, doublereal *),
vsubg_(doublereal *, doublereal *, integer *, doublereal *);
doublereal stemp[6];
extern logical eqstr_(char *, char *, ftnlen, ftnlen);
doublereal xform[36] /* was [6][6] */;
logical uselt;
extern /* Subroutine */ int bodc2s_(integer *, char *, ftnlen);
doublereal ssbtg0[6];
extern logical failed_(void);
doublereal sa[3];
extern /* Subroutine */ int cleard_(integer *, doublereal *);
doublereal lt;
integer frcode;
extern doublereal clight_(void);
extern logical return_(void);
doublereal corxfi[36] /* was [6][6] */, corxfm[36] /* was [6][6]
*/, fxosta[6], fxpsta[6], fxpvel[3], fxtsta[6], obspnt[6], obssta[
12] /* was [6][2] */, obstrg[6], acc[3], pntsta[6], raysta[6],
sastat[6], spoint[3], srfvec[3], ssbobs[6], ssbtrg[6], trgepc;
integer center, clssid, frclss;
logical attblk[6], usestl;
extern /* Subroutine */ int setmsg_(char *, ftnlen);
logical fnd;
extern /* Subroutine */ int sigerr_(char *, ftnlen), chkout_(char *,
ftnlen), namfrm_(char *, integer *, ftnlen), frinfo_(integer *,
integer *, integer *, integer *, logical *), errint_(char *,
integer *, ftnlen), spkgeo_(integer *, doublereal *, char *,
integer *, doublereal *, doublereal *, ftnlen), vminug_(
doublereal *, integer *, doublereal *), dnearp_(doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *, logical *), surfpv_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *, logical *)
, subpnt_(char *, char *, doublereal *, char *, char *, char *,
doublereal *, doublereal *, doublereal *, ftnlen, ftnlen, ftnlen,
ftnlen, ftnlen), spkssb_(integer *, doublereal *, char *,
doublereal *, ftnlen);
doublereal dlt;
extern /* Subroutine */ int sxform_(char *, char *, doublereal *,
doublereal *, ftnlen, ftnlen), qderiv_(integer *, doublereal *,
doublereal *, doublereal *, doublereal *), invstm_(doublereal *,
doublereal *);
/* $ Abstract */
/* SPICE private routine intended solely for the support of SPICE */
/* routines. Users should not call this routine directly due to the */
/* volatile nature of this routine. */
/* Return the state of a sub-observer point used to define */
/* coordinates referenced in a GF search. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* GF */
/* SPK */
/* TIME */
/* NAIF_IDS */
/* FRAMES */
/* $ Keywords */
/* GEOMETRY */
/* PRIVATE */
/* SEARCH */
/* $ Declarations */
/* $ Abstract */
/* This file contains public, global parameter declarations */
/* for the SPICELIB Geometry Finder (GF) subsystem. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* GF */
/* $ Keywords */
/* GEOMETRY */
/* ROOT */
/* $ Restrictions */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* L.E. Elson (JPL) */
/* E.D. Wright (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.3.0, 01-OCT-2011 (NJB) */
/* Added NWILUM parameter. */
/* - SPICELIB Version 1.2.0, 14-SEP-2010 (EDW) */
/* Added NWPA parameter. */
/* - SPICELIB Version 1.1.0, 08-SEP-2009 (EDW) */
/* Added NWRR parameter. */
/* Added NWUDS parameter. */
/* - SPICELIB Version 1.0.0, 21-FEB-2009 (NJB) (LSE) (EDW) */
/* -& */
/* Root finding parameters: */
/* CNVTOL is the default convergence tolerance used by the */
/* high-level GF search API routines. This tolerance is */
/* used to terminate searches for binary state transitions: */
/* when the time at which a transition occurs is bracketed */
/* by two times that differ by no more than CNVTOL, the */
/* transition time is considered to have been found. */
/* Units are TDB seconds. */
/* NWMAX is the maximum number of windows allowed for user-defined */
/* workspace array. */
/* DOUBLE PRECISION WORK ( LBCELL : MW, NWMAX ) */
/* Currently no more than twelve windows are required; the three */
/* extra windows are spares. */
/* Callers of GFEVNT can include this file and use the parameter */
/* NWMAX to declare the second dimension of the workspace array */
/* if necessary. */
/* Callers of GFIDST should declare their workspace window */
/* count using NWDIST. */
/* Callers of GFSEP should declare their workspace window */
/* count using NWSEP. */
/* Callers of GFRR should declare their workspace window */
/* count using NWRR. */
/* Callers of GFUDS should declare their workspace window */
/* count using NWUDS. */
/* Callers of GFPA should declare their workspace window */
/* count using NWPA. */
/* Callers of GFILUM should declare their workspace window */
/* count using NWILUM. */
/* ADDWIN is a parameter used to expand each interval of the search */
/* (confinement) window by a small amount at both ends in order to */
/* accommodate searches using equality constraints. The loaded */
/* kernel files must accommodate these expanded time intervals. */
/* FRMNLN is a string length for frame names. */
/* NVRMAX is the maximum number of vertices if FOV type is "POLYGON" */
/* FOVTLN -- maximum length for FOV string. */
/* Specify the character strings that are allowed in the */
/* specification of field of view shapes. */
/* Character strings that are allowed in the */
/* specification of occultation types: */
/* Occultation target shape specifications: */
/* Specify the number of supported occultation types and occultation */
/* type string length: */
/* Instrument field-of-view (FOV) parameters */
/* Maximum number of FOV boundary vectors: */
/* FOV shape parameters: */
/* circle */
/* ellipse */
/* polygon */
/* rectangle */
/* End of file gf.inc. */
/* $ Abstract */
/* SPICE private include file intended solely for the support of */
/* SPICE routines. Users should not include this routine in their */
/* source code due to the volatile nature of this file. */
/* This file contains private, global parameter declarations */
/* for the SPICELIB Geometry Finder (GF) subsystem. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* GF */
/* $ Keywords */
/* GEOMETRY */
/* ROOT */
/* $ Restrictions */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* E.D. Wright (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 17-FEB-2009 (NJB) (EDW) */
/* -& */
/* The set of supported coordinate systems */
/* System Coordinates */
/* ---------- ----------- */
/* Rectangular X, Y, Z */
/* Latitudinal Radius, Longitude, Latitude */
/* Spherical Radius, Colatitude, Longitude */
/* RA/Dec Range, Right Ascension, Declination */
/* Cylindrical Radius, Longitude, Z */
/* Geodetic Longitude, Latitude, Altitude */
/* Planetographic Longitude, Latitude, Altitude */
/* Below we declare parameters for naming coordinate systems. */
/* User inputs naming coordinate systems must match these */
/* when compared using EQSTR. That is, user inputs must */
/* match after being left justified, converted to upper case, */
/* and having all embedded blanks removed. */
/* Below we declare names for coordinates. Again, user */
/* inputs naming coordinates must match these when */
/* compared using EQSTR. */
/* Note that the RA parameter value below matches */
/* 'RIGHT ASCENSION' */
/* when extra blanks are compressed out of the above value. */
/* Parameters specifying types of vector definitions */
/* used for GF coordinate searches: */
/* All string parameter values are left justified, upper */
/* case, with extra blanks compressed out. */
/* POSDEF indicates the vector is defined by the */
/* position of a target relative to an observer. */
/* SOBDEF indicates the vector points from the center */
/* of a target body to the sub-observer point on */
/* that body, for a given observer and target. */
/* SOBDEF indicates the vector points from the center */
/* of a target body to the surface intercept point on */
/* that body, for a given observer, ray, and target. */
/* Number of workspace windows used by ZZGFREL: */
/* Number of additional workspace windows used by ZZGFLONG: */
/* Index of "existence window" used by ZZGFCSLV: */
/* Progress report parameters: */
/* MXBEGM, */
/* MXENDM are, respectively, the maximum lengths of the progress */
/* report message prefix and suffix. */
/* Note: the sum of these lengths, plus the length of the */
/* "percent complete" substring, should not be long enough */
/* to cause wrap-around on any platform's terminal window. */
/* Total progress report message length upper bound: */
/* End of file zzgf.inc. */
/* $ Abstract */
/* Include file zzabcorr.inc */
/* SPICE private file intended solely for the support of SPICE */
/* routines. Users should not include this file directly due */
/* to the volatile nature of this file */
/* The parameters below define the structure of an aberration */
/* correction attribute block. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Parameters */
/* An aberration correction attribute block is an array of logical */
/* flags indicating the attributes of the aberration correction */
/* specified by an aberration correction string. The attributes */
/* are: */
/* - Is the correction "geometric"? */
/* - Is light time correction indicated? */
/* - Is stellar aberration correction indicated? */
/* - Is the light time correction of the "converged */
/* Newtonian" variety? */
/* - Is the correction for the transmission case? */
/* - Is the correction relativistic? */
/* The parameters defining the structure of the block are as */
/* follows: */
/* NABCOR Number of aberration correction choices. */
/* ABATSZ Number of elements in the aberration correction */
/* block. */
/* GEOIDX Index in block of geometric correction flag. */
/* LTIDX Index of light time flag. */
/* STLIDX Index of stellar aberration flag. */
/* CNVIDX Index of converged Newtonian flag. */
/* XMTIDX Index of transmission flag. */
/* RELIDX Index of relativistic flag. */
/* The following parameter is not required to define the block */
/* structure, but it is convenient to include it here: */
/* CORLEN The maximum string length required by any aberration */
/* correction string */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 18-DEC-2004 (NJB) */
/* -& */
/* Number of aberration correction choices: */
/* Aberration correction attribute block size */
/* (number of aberration correction attributes): */
/* Indices of attributes within an aberration correction */
/* attribute block: */
/* Maximum length of an aberration correction string: */
/* End of include file zzabcorr.inc */
/* $ Brief_I/O */
/* VARIABLE I/O DESCRIPTION */
/* -------- --- -------------------------------------------------- */
/* METHOD I Computation method. */
/* TRGID I Target ID code. */
/* ET I Computation epoch. */
/* FIXREF I Reference frame name. */
/* ABCORR I Aberration correction. */
/* OBSID I Observer ID code. */
/* RADII I Target radii. */
/* STATE O State used to define coordinates. */
/* $ Detailed_Input */
/* METHOD is a short string providing parameters defining */
/* the computation method to be used. Any value */
/* supported by SUBPNT may be used. */
/* TRGID is the NAIF ID code of the target object. */
/* *This routine assumes that the target is modeled */
/* as a tri-axial ellipsoid.* */
/* ET is the time, expressed as ephemeris seconds past J2000 */
/* TDB, at which the specified state is to be computed. */
/* FIXREF is the name of the reference frame relative to which */
/* the state of interest is specified. */
/* FIXREF must be centered on the target body. */
/* Case, leading and trailing blanks are not significant */
/* in the string FIXREF. */
/* ABCORR indicates the aberration corrections to be applied to */
/* the state of the target body to account for one-way */
/* light time and stellar aberration. The orientation */
/* of the target body will also be corrected for one-way */
/* light time when light time corrections are requested. */
/* Supported aberration correction options for */
/* observation (case where radiation is received by */
/* observer at ET) are: */
/* NONE No correction. */
/* LT Light time only. */
/* LT+S Light time and stellar aberration. */
/* CN Converged Newtonian (CN) light time. */
/* CN+S CN light time and stellar aberration. */
/* Supported aberration correction options for */
/* transmission (case where radiation is emitted from */
/* observer at ET) are: */
/* XLT Light time only. */
/* XLT+S Light time and stellar aberration. */
/* XCN Converged Newtonian (CN) light time. */
/* XCN+S CN light time and stellar aberration. */
/* For detailed information, see the geometry finder */
/* required reading, gf.req. Also see the header of */
/* SPKEZR, which contains a detailed discussion of */
/* aberration corrections. */
/* Case, leading and trailing blanks are not significant */
/* in the string ABCORR. */
/* OBSID is the NAIF ID code of the observer. */
/* RADII is an array containing three radii defining */
/* a reference ellipsoid for the target body. */
/* $ Detailed_Output */
/* STATE is the state of the sub-observer point at ET. */
/* The first three components of STATE contain the */
/* sub-observer point itself; the last three */
/* components contain the derivative with respect to */
/* time of the position. The state is expressed */
/* relative to the body-fixed frame designated by */
/* FIXREF. */
/* Units are km and km/s. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If the aberration correction ABCORR is not recognized, */
/* the error will be diagnosed by routines in the call tree */
/* of this routine. */
/* 2) If the frame FIXREF is not recognized by the frames */
/* subsystem, the error will be diagnosed by routines in the */
/* call tree of this routine. */
/* 3) FIXREF must be centered on the target body; if it isn't, */
/* the error will be diagnosed by routines in the call tree */
/* of this routine. */
/* 4) Any error that occurs while look up the state of the target */
/* or observer will be diagnosed by routines in the call tree of */
/* this routine. */
/* 5) Any error that occurs while look up the orientation of */
/* the target will be diagnosed by routines in the call tree of */
/* this routine. */
/* 6) If the input method is not recognized, the error */
/* SPICE(NOTSUPPORTED) will be signaled. */
/* $ Files */
/* Appropriate kernels must be loaded by the calling program before */
/* this routine is called. */
/* The following data are required: */
/* - SPK data: ephemeris data for target and observer must be */
/* loaded. If aberration corrections are used, the states of */
/* target and observer relative to the solar system barycenter */
/* must be calculable from the available ephemeris data. */
/* Typically ephemeris data are made available by loading one */
/* or more SPK files via FURNSH. */
/* - PCK data: if the target body shape is modeled as an */
/* ellipsoid, triaxial radii for the target body must be loaded */
/* into the kernel pool. Typically this is done by loading a */
/* text PCK file via FURNSH. */
/* - Further PCK data: rotation data for the target body must be */
/* loaded. These may be provided in a text or binary PCK file. */
/* - Frame data: if a frame definition is required to convert the */
/* observer and target states to the body-fixed frame of the */
/* target, that definition must be available in the kernel */
/* pool. Typically the definition is supplied by loading a */
/* frame kernel via FURNSH. */
/* In all cases, kernel data are normally loaded once per program */
/* run, NOT every time this routine is called. */
/* $ Particulars */
/* This routine isolates the computation of the sub-observer state */
/* (that is, the sub-observer point and its derivative with respect */
/* to time). */
/* This routine is used by the GF coordinate utility routines in */
/* order to solve for time windows on which specified mathematical */
/* conditions involving coordinates are satisfied. The role of */
/* this routine is to provide Cartesian state vectors enabling */
/* the GF coordinate utilities to determine the signs of the */
/* derivatives with respect to time of coordinates of interest. */
/* $ Examples */
/* See ZZGFCOST. */
/* $ Restrictions */
/* 1) This routine is restricted to use with ellipsoidal target */
/* shape models. */
/* 2) The computations performed by this routine are intended */
/* to be compatible with those performed by the SPICE */
/* routine SUBPNT. If that routine changes, this routine */
/* may need to be updated. */
/* 3) This routine presumes that error checking of inputs */
/* has, where possible, already been performed by the */
/* GF coordinate utility initialization routine. */
/* 4) The interface and functionality of this set of routines may */
/* change without notice. These routines should be called only */
/* by SPICELIB routines. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Version */
/* - SPICELIB Version 2.0.0 12-MAY-2009 (NJB) */
/* Upgraded to support targets and observers having */
/* no names associated with their ID codes. */
/* - SPICELIB Version 1.0.0 05-MAR-2009 (NJB) */
/* -& */
/* $ Index_Entries */
/* sub-observer state */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
}
chkin_("ZZGFSSOB", (ftnlen)8);
if (first || *trgid != prvtrg) {
bodc2s_(trgid, svtarg, (ftnlen)36);
prvtrg = *trgid;
}
if (first || *obsid != prvobs) {
bodc2s_(obsid, svobs, (ftnlen)36);
prvobs = *obsid;
}
first = FALSE_;
/* Parse the aberration correction specifier. */
zzprscor_(abcorr, attblk, abcorr_len);
geom = attblk[0];
uselt = attblk[1];
usestl = attblk[2];
xmit = attblk[4];
/* Decide whether the sub-observer point is computed using */
/* the "near point" or "surface intercept" method. Only */
/* ellipsoids may be used a shape models for this computation. */
if (eqstr_(method, "Near point: ellipsoid", method_len, (ftnlen)21)) {
near__ = TRUE_;
} else if (eqstr_(method, "Intercept: ellipsoid", method_len, (ftnlen)20))
{
near__ = FALSE_;
} else {
setmsg_("Sub-observer point computation method # is not supported by"
" this routine.", (ftnlen)73);
errch_("#", method, (ftnlen)1, method_len);
sigerr_("SPICE(NOTSUPPORTED)", (ftnlen)19);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
if (geom) {
/* This is the geometric case. */
/* We need to check the body-fixed reference frame here. */
namfrm_(fixref, &frcode, fixref_len);
frinfo_(&frcode, ¢er, &frclss, &clssid, &fnd);
if (failed_()) {
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
if (! fnd) {
setmsg_("Input reference frame # was not recognized.", (ftnlen)43)
;
errch_("#", fixref, (ftnlen)1, fixref_len);
sigerr_("SPICE(NOFRAME)", (ftnlen)14);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
if (center != *trgid) {
setmsg_("Input reference frame # is centered on body # instead o"
"f body #.", (ftnlen)64);
errch_("#", fixref, (ftnlen)1, fixref_len);
errint_("#", ¢er, (ftnlen)1);
errint_("#", trgid, (ftnlen)1);
sigerr_("SPICE(INVALIDFRAME)", (ftnlen)19);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
/* Get the state of the target with respect to the observer, */
/* expressed relative to the target body-fixed frame. We don't */
/* need to propagate states to the solar system barycenter in */
/* this case. */
spkgeo_(trgid, et, fixref, obsid, fxtsta, <, fixref_len);
if (failed_()) {
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
/* Compute the state of the observer with respect to the target */
/* in the body-fixed frame. */
vminug_(fxtsta, &c__6, fxosta);
/* Now we can obtain the surface velocity of the sub-observer */
/* point. */
if (near__) {
/* The sub-observer point method is "near point." */
dnearp_(fxosta, radii, &radii[1], &radii[2], fxpsta, dalt, &found)
;
if (! found) {
setmsg_("The sub-observer state could could not be computed "
"because the velocity was not well defined. DNEARP re"
"turned \"not found.\"", (ftnlen)122);
sigerr_("SPICE(DEGENERATECASE)", (ftnlen)21);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
} else {
/* The sub-observer point method is "surface */
/* intercept point." The ray direction is simply */
/* the negative of the observer's position relative */
/* to the target center. */
vminug_(fxosta, &c__6, raysta);
surfpv_(fxosta, raysta, radii, &radii[1], &radii[2], fxpsta, &
found);
/* Although in general it's not an error for SURFPV to */
/* be unable to compute an intercept state, it *is* */
/* an error in this case, since the ray points toward */
/* the center of the target. */
if (! found) {
setmsg_("The sub-observer state could could not be computed "
"because the velocity was not well defined. SURFPV re"
"turned \"not found.\"", (ftnlen)122);
sigerr_("SPICE(DEGENERATECASE)", (ftnlen)21);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
}
} else if (uselt) {
/* Light time and possibly stellar aberration corrections are */
/* applied. */
/* Most our work consists of getting ready to call either of the */
/* SPICELIB routines DNEARP or SURFPV. In order to make this */
/* call, we'll need the velocity of the observer relative to the */
/* target body's center in the target body-fixed frame. We must */
/* evaluate the rotation state of the target at the correct */
/* epoch, and account for the rate of change of light time, if */
/* light time corrections are used. The algorithm we use depends */
/* on the algorithm used in SUBPNT, since we're computing the */
/* derivative with respect to time of the solution found by that */
/* routine. */
/* In this algorithm, we must take into account the fact that */
/* SUBPNT performs light time and stellar aberration corrections */
/* for the sub-observer point, not for the center of the target */
/* body. */
/* If light time and stellar aberration corrections are used, */
/* - Find the aberration corrected sub-observer point and the */
/* light time-corrected epoch TRGEPC associated with the */
/* sub-observer point. */
/* - Use TRGEPC to find the position of the target relative to */
/* the solar system barycenter. */
/* - Use TRGEPC to find the orientation of the target relative */
/* to the J2000 reference frame. */
/* - Find the light-time corrected position of the */
/* sub-observer point; use this to compute the stellar */
/* aberration offset that applies to the sub-observer point, */
/* as well as the velocity of this offset. */
/* - Find the corrected state of the target center as seen */
/* from the observer, where the corrections are those */
/* applicable to the sub-observer point. */
/* - Negate the corrected target center state to obtain the */
/* state of the observer relative to the target. */
/* - Express the state of the observer relative to the target */
/* in the target body fixed frame at TRGEPC. */
/* Below, we'll use the convention that vectors expressed */
/* relative to the body-fixed frame have names of the form */
/* FX* */
/* Note that SUBPNT will signal an error if FIXREF is not */
/* actually centered on the target body. */
subpnt_(method, svtarg, et, fixref, abcorr, svobs, spoint, &trgepc,
srfvec, method_len, (ftnlen)36, fixref_len, abcorr_len, (
ftnlen)36);
/* Get J2000-relative states of observer and target with respect */
/* to the solar system barycenter at their respective epochs of */
/* participation. */
spkssb_(obsid, et, "J2000", ssbobs, (ftnlen)5);
spkssb_(trgid, &trgepc, "J2000", ssbtg0, (ftnlen)5);
/* Get the uncorrected J2000 to body-fixed to state */
/* transformation at TRGEPC. */
sxform_("J2000", fixref, &trgepc, xform, (ftnlen)5, fixref_len);
if (failed_()) {
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
/* Initialize the state of the sub-observer point in the */
/* body-fixed frame. At this point we don't know the */
/* point's velocity; set it to zero. */
moved_(spoint, &c__3, fxpsta);
cleard_(&c__3, &fxpsta[3]);
if (usestl) {
/* We're going to need the acceleration of the observer */
/* relative to the SSB. Compute this now. */
for (i__ = 1; i__ <= 2; ++i__) {
/* The epoch is ET -/+ TDELTA. */
t = *et + ((i__ << 1) - 3) * 1.;
spkssb_(obsid, &t, "J2000", &obssta[(i__1 = i__ * 6 - 6) < 12
&& 0 <= i__1 ? i__1 : s_rnge("obssta", i__1, "zzgfss"
"ob_", (ftnlen)652)], (ftnlen)5);
}
if (failed_()) {
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
/* Compute the observer's acceleration using a quadratic */
/* approximation. */
qderiv_(&c__3, &obssta[3], &obssta[9], &c_b40, acc);
}
/* The rest of the algorithm is iterative. On the first */
/* iteration, we don't have a good estimate of the velocity */
/* of the sub-observer point relative to the body-fixed */
/* frame. Since we're using this velocity as an input */
/* to the aberration velocity computations, we */
/* expect that treating this velocity as zero on the first */
/* pass yields a reasonable estimate. On the second pass, */
/* we'll use the velocity derived on the first pass. */
cleard_(&c__3, fxpvel);
/* We'll also estimate the rate of change of light time */
/* as zero on the first pass. */
dlt = 0.;
for (i__ = 1; i__ <= 2; ++i__) {
/* Correct the target's velocity for the rate of */
/* change of light time. */
if (xmit) {
scale = dlt + 1.;
} else {
scale = 1. - dlt;
}
/* Scale the velocity portion of the target state to */
/* correct the velocity for the rate of change of light */
/* time. */
moved_(ssbtg0, &c__3, ssbtrg);
vscl_(&scale, &ssbtg0[3], &ssbtrg[3]);
/* Get the state of the target with respect to the observer. */
vsubg_(ssbtrg, ssbobs, &c__6, obstrg);
/* Correct the J2000 to body-fixed state transformation matrix */
/* for the rate of change of light time. */
zzcorsxf_(&xmit, &dlt, xform, corxfm);
/* Invert CORXFM to obtain the corrected */
/* body-fixed to J2000 state transformation. */
invstm_(corxfm, corxfi);
/* Convert the sub-observer point state to the J2000 frame. */
mxvg_(corxfi, fxpsta, &c__6, &c__6, pntsta);
/* Find the J2000-relative state of the sub-observer */
/* point with respect to the target. */
vaddg_(obstrg, pntsta, &c__6, obspnt);
if (usestl) {
/* Now compute the stellar aberration correction */
/* applicable to OBSPNT. We need the velocity of */
/* this correction as well. */
zzstelab_(&xmit, acc, &ssbobs[3], obspnt, sa, savel);
moved_(sa, &c__3, sastat);
moved_(savel, &c__3, &sastat[3]);
/* Adding the stellar aberration state to the target center */
/* state gives us the state of the target center with */
/* respect to the observer, corrected for the aberrations */
/* applicable to the sub-observer point. */
vaddg_(obstrg, sastat, &c__6, stemp);
} else {
moved_(obstrg, &c__6, stemp);
}
/* Convert STEMP to the body-fixed reference frame. */
mxvg_(corxfm, stemp, &c__6, &c__6, fxtsta);
/* At long last, compute the state of the observer */
/* with respect to the target in the body-fixed frame. */
vminug_(fxtsta, &c__6, fxosta);
/* Now we can obtain the surface velocity of the */
/* sub-observer point. */
if (near__) {
/* The sub-observer point method is "near point." */
dnearp_(fxosta, radii, &radii[1], &radii[2], fxpsta, dalt, &
found);
if (! found) {
setmsg_("The sub-observer state could could not be compu"
"ted because the velocity was not well defined. "
"DNEARP returned \"not found.\"", (ftnlen)123);
sigerr_("SPICE(DEGENERATECASE)", (ftnlen)21);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
} else {
/* The sub-observer point method is "surface intercept */
/* point." The ray direction is simply the negative of the */
/* observer's position relative to the target center. */
vminug_(fxosta, &c__6, raysta);
surfpv_(fxosta, raysta, radii, &radii[1], &radii[2], fxpsta, &
found);
/* Although in general it's not an error for SURFPV to be */
/* unable to compute an intercept state, it *is* an error */
/* in this case, since the ray points toward the center of */
/* the target. */
if (! found) {
setmsg_("The sub-observer state could could not be compu"
"ted because the velocity was not well defined. S"
"URFPV returned \"not found.\"", (ftnlen)122);
sigerr_("SPICE(DEGENERATECASE)", (ftnlen)21);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
}
/* At this point we can update the surface point */
/* velocity and light time derivative estimates. */
/* In order to compute the light time rate, we'll */
/* need the J2000-relative velocity of the sub-observer */
/* point with respect to the observer. First convert */
/* the sub-observer state to the J2000 frame, then */
/* add the result to the state of the target center */
/* with respect to the observer. */
mxvg_(corxfi, fxpsta, &c__6, &c__6, pntsta);
vaddg_(obstrg, pntsta, &c__6, obspnt);
/* Now that we have an improved estimate of the */
/* sub-observer state, we can estimate the rate of */
/* change of light time as */
/* range rate */
/* ---------- */
/* c */
/* If we're correcting for stellar aberration, *ideally* we */
/* should remove that correction now, since the light time */
/* rate is based on light time between the observer and the */
/* light-time corrected sub-observer point. But the error made */
/* by including stellar aberration is too small to make it */
/* worthwhile to make this adjustment. */
vhat_(obspnt, upos);
dlt = vdot_(&obspnt[3], upos) / clight_();
/* With FXPVEL and DLT updated, we'll repeat our */
/* computations. */
}
} else {
/* We should never get here. */
setmsg_("Aberration correction # was not recognized.", (ftnlen)43);
errch_("#", abcorr, (ftnlen)1, abcorr_len);
sigerr_("SPICE(NOTSUPPORTED)", (ftnlen)19);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
}
/* Copy the computed state to the output argument STATE. */
moved_(fxpsta, &c__6, state);
chkout_("ZZGFSSOB", (ftnlen)8);
return 0;
} /* zzgfssob_ */
/* $Procedure SPKLTC ( S/P Kernel, light time corrected state ) */
/* Subroutine */ int spkltc_(integer *targ, doublereal *et, char *ref, char *
abcorr, doublereal *stobs, doublereal *starg, doublereal *lt,
doublereal *dlt, ftnlen ref_len, ftnlen abcorr_len)
{
/* Initialized data */
static logical pass1 = TRUE_;
static char prvcor[5] = " ";
/* System generated locals */
doublereal d__1, d__2, d__3, d__4;
/* Builtin functions */
integer s_cmp(char *, char *, ftnlen, ftnlen);
/* Subroutine */ int s_copy(char *, char *, ftnlen, ftnlen);
/* Local variables */
doublereal dist;
extern doublereal vdot_(doublereal *, doublereal *);
static logical xmit;
extern /* Subroutine */ int zzvalcor_(char *, logical *, ftnlen);
doublereal a, b, c__;
integer i__, refid;
extern /* Subroutine */ int chkin_(char *, ftnlen);
doublereal epoch;
extern /* Subroutine */ int errch_(char *, char *, ftnlen, ftnlen);
static logical usecn;
extern /* Subroutine */ int vlcom_(doublereal *, doublereal *, doublereal
*, doublereal *, doublereal *), vsubg_(doublereal *, doublereal *,
integer *, doublereal *);
doublereal ssblt, lterr;
static logical uselt;
extern doublereal vnorm_(doublereal *);
doublereal prvlt;
extern logical failed_(void);
extern doublereal clight_(void);
logical attblk[15];
extern doublereal touchd_(doublereal *);
extern /* Subroutine */ int spkgeo_(integer *, doublereal *, char *,
integer *, doublereal *, doublereal *, ftnlen), sigerr_(char *,
ftnlen), chkout_(char *, ftnlen);
integer ltsign;
extern /* Subroutine */ int irfnum_(char *, integer *, ftnlen), setmsg_(
char *, ftnlen);
doublereal ssbtrg[6];
integer numitr;
extern logical return_(void);
logical usestl;
/* $ Abstract */
/* Return the state (position and velocity) of a target body */
/* relative to an observer, optionally corrected for light time, */
/* expressed relative to an inertial reference frame. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* SPK */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Abstract */
/* Include file zzabcorr.inc */
/* SPICE private file intended solely for the support of SPICE */
/* routines. Users should not include this file directly due */
/* to the volatile nature of this file */
/* The parameters below define the structure of an aberration */
/* correction attribute block. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Parameters */
/* An aberration correction attribute block is an array of logical */
/* flags indicating the attributes of the aberration correction */
/* specified by an aberration correction string. The attributes */
/* are: */
/* - Is the correction "geometric"? */
/* - Is light time correction indicated? */
/* - Is stellar aberration correction indicated? */
/* - Is the light time correction of the "converged */
/* Newtonian" variety? */
/* - Is the correction for the transmission case? */
/* - Is the correction relativistic? */
/* The parameters defining the structure of the block are as */
/* follows: */
/* NABCOR Number of aberration correction choices. */
/* ABATSZ Number of elements in the aberration correction */
/* block. */
/* GEOIDX Index in block of geometric correction flag. */
/* LTIDX Index of light time flag. */
/* STLIDX Index of stellar aberration flag. */
/* CNVIDX Index of converged Newtonian flag. */
/* XMTIDX Index of transmission flag. */
/* RELIDX Index of relativistic flag. */
/* The following parameter is not required to define the block */
/* structure, but it is convenient to include it here: */
/* CORLEN The maximum string length required by any aberration */
/* correction string */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 1.0.0, 18-DEC-2004 (NJB) */
/* -& */
/* Number of aberration correction choices: */
/* Aberration correction attribute block size */
/* (number of aberration correction attributes): */
/* Indices of attributes within an aberration correction */
/* attribute block: */
/* Maximum length of an aberration correction string: */
/* End of include file zzabcorr.inc */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* TARG I Target body. */
/* ET I Observer epoch. */
/* REF I Inertial reference frame of output state. */
/* ABCORR I Aberration correction flag. */
/* STOBS I State of the observer relative to the SSB. */
/* STARG O State of target. */
/* LT O One way light time between observer and target. */
/* DLT O Derivative of light time with respect to time. */
/* $ Detailed_Input */
/* TARG is the NAIF ID code for a target body. The target */
/* and observer define a state vector whose position */
/* component points from the observer to the target. */
/* ET is the ephemeris time, expressed as seconds past */
/* J2000 TDB, at which the state of the target body */
/* relative to the observer is to be computed. ET */
/* refers to time at the observer's location. */
/* REF is the inertial reference frame with respect to which */
/* the input state STOBS and the output state STARG are */
/* expressed. REF must be recognized by the SPICE */
/* Toolkit. The acceptable frames are listed in the */
/* Frames Required Reading, as well as in the SPICELIB */
/* routine CHGIRF. */
/* Case and blanks are not significant in the string */
/* REF. */
/* ABCORR indicates the aberration corrections to be applied to */
/* the state of the target body to account for one-way */
/* light time. See the discussion in the Particulars */
/* section for recommendations on how to choose */
/* aberration corrections. */
/* If ABCORR includes the stellar aberration correction */
/* symbol '+S', this flag is simply ignored. Aside from */
/* the possible presence of this symbol, ABCORR may be */
/* any of the following: */
/* 'NONE' Apply no correction. Return the */
/* geometric state of the target body */
/* relative to the observer. */
/* The following values of ABCORR apply to the */
/* "reception" case in which photons depart from the */
/* target's location at the light-time corrected epoch */
/* ET-LT and *arrive* at the observer's location at ET: */
/* 'LT' Correct for one-way light time (also */
/* called "planetary aberration") using a */
/* Newtonian formulation. This correction */
/* yields the state of the target at the */
/* moment it emitted photons arriving at */
/* the observer at ET. */
/* The light time correction involves */
/* iterative solution of the light time */
/* equation (see Particulars for details). */
/* The solution invoked by the 'LT' option */
/* uses one iteration. */
/* 'CN' Converged Newtonian light time */
/* correction. In solving the light time */
/* equation, the 'CN' correction iterates */
/* until the solution converges (three */
/* iterations on all supported platforms). */
/* Whether the 'CN+S' solution is */
/* substantially more accurate than the */
/* 'LT' solution depends on the geometry */
/* of the participating objects and on the */
/* accuracy of the input data. In all */
/* cases this routine will execute more */
/* slowly when a converged solution is */
/* computed. See the Particulars section of */
/* SPKEZR for a discussion of precision of */
/* light time corrections. */
/* The following values of ABCORR apply to the */
/* "transmission" case in which photons *depart* from */
/* the observer's location at ET and arrive at the */
/* target's location at the light-time corrected epoch */
/* ET+LT: */
/* 'XLT' "Transmission" case: correct for */
/* one-way light time using a Newtonian */
/* formulation. This correction yields the */
/* state of the target at the moment it */
/* receives photons emitted from the */
/* observer's location at ET. */
/* 'XCN' "Transmission" case: converged */
/* Newtonian light time correction. */
/* Neither special nor general relativistic effects are */
/* accounted for in the aberration corrections applied */
/* by this routine. */
/* Case and blanks are not significant in the string */
/* ABCORR. */
/* STOBS is the geometric (uncorrected) state of the observer */
/* relative to the solar system barycenter at epoch ET. */
/* STOBS is a 6-vector: the first three components of */
/* STOBS represent a Cartesian position vector; the last */
/* three components represent the corresponding velocity */
/* vector. STOBS is expressed relative to the inertial */
/* reference frame designated by REF. */
/* Units are always km and km/sec. */
/* $ Detailed_Output */
/* STARG is a Cartesian state vector representing the position */
/* and velocity of the target body relative to the */
/* specified observer. STARG is corrected for the */
/* specified aberration, and is expressed with respect */
/* to the specified inertial reference frame. The first */
/* three components of STARG represent the x-, y- and */
/* z-components of the target's position; last three */
/* components form the corresponding velocity vector. */
/* The position component of STARG points from the */
/* observer's location at ET to the aberration-corrected */
/* location of the target. Note that the sense of the */
/* position vector is independent of the direction of */
/* radiation travel implied by the aberration */
/* correction. */
/* Units are always km and km/sec. */
/* LT is the one-way light time between the observer and */
/* target in seconds. If the target state is corrected */
/* for light time, then LT is the one-way light time */
/* between the observer and the light time-corrected */
/* target location. */
/* DLT is the derivative with respect to barycentric */
/* dynamical time of the one way light time between */
/* target and observer: */
/* DLT = d(LT)/d(ET) */
/* DLT can also be described as the rate of change of */
/* one way light time. DLT is unitless, since LT and */
/* ET both have units of TDB seconds. */
/* If the observer and target are at the same position, */
/* then DLT is set to zero. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) For the convenience of the caller, the input aberration */
/* correction flag can call for stellar aberration correction via */
/* inclusion of the '+S' suffix. This portion of the aberration */
/* correction flag is ignored if present. */
/* 2) If the value of ABCORR is not recognized, the error */
/* is diagnosed by a routine in the call tree of this */
/* routine. */
/* 3) If the reference frame requested is not a recognized */
/* inertial reference frame, the error SPICE(BADFRAME) */
/* is signaled. */
/* 4) If the state of the target relative to the solar system */
/* barycenter cannot be computed, the error will be diagnosed */
/* by routines in the call tree of this routine. */
/* 5) If the observer and target are at the same position, */
/* then DLT is set to zero. This situation could arise, */
/* for example, when the observer is Mars and the target */
/* is the Mars barycenter. */
/* 6) If a division by zero error would occur in the computation */
/* of DLT, the error SPICE(DIVIDEBYZERO) is signaled. */
/* $ Files */
/* This routine computes states using SPK files that have been */
/* loaded into the SPICE system, normally via the kernel loading */
/* interface routine FURNSH. Application programs typically load */
/* kernels once before this routine is called, for example during */
/* program initialization; kernels need not be loaded repeatedly. */
/* See the routine FURNSH and the SPK and KERNEL Required Reading */
/* for further information on loading (and unloading) kernels. */
/* If any of the ephemeris data used to compute STARG are expressed */
/* relative to a non-inertial frame in the SPK files providing those */
/* data, additional kernels may be needed to enable the reference */
/* frame transformations required to compute the state. Normally */
/* these additional kernels are PCK files or frame kernels. Any */
/* such kernels must already be loaded at the time this routine is */
/* called. */
/* $ Particulars */
/* This routine supports higher-level SPK API routines that can */
/* perform both light time and stellar aberration corrections. */
/* User applications normally will not need to call this routine */
/* directly. */
/* See the header of the routine SPKEZR for a detailed discussion */
/* of aberration corrections. */
/* $ Examples */
/* The numerical results shown for this example may differ across */
/* platforms. The results depend on the SPICE kernels used as */
/* input, the compiler and supporting libraries, and the machine */
/* specific arithmetic implementation. */
/* 1) Look up a sequence of states of the Moon as seen from the */
/* Earth. Use light time corrections. Compute the first state for */
/* the epoch 2000 JAN 1 12:00:00 TDB; compute subsequent states at */
/* intervals of 1 hour. For each epoch, display the states, the */
/* one way light time between target and observer, and the rate of */
/* change of the one way light time. */
/* Use the following meta-kernel to specify the kernels to */
/* load: */
/* KPL/MK */
/* File name: spkltc.tm */
/* This meta-kernel is intended to support operation of SPICE */
/* example programs. The kernels shown here should not be */
/* assumed to contain adequate or correct versions of data */
/* required by SPICE-based user applications. */
/* In order for an application to use this meta-kernel, the */
/* kernels referenced here must be present in the user's */
/* current working directory. */
/* \begindata */
/* KERNELS_TO_LOAD = ( 'de421.bsp', */
/* 'pck00010.tpc', */
/* 'naif0010.tls' ) */
/* \begintext */
/* The code example follows: */
/* PROGRAM EX1 */
/* IMPLICIT NONE */
/* C */
/* C Local constants */
/* C */
/* C The meta-kernel name shown here refers to a file whose */
/* C contents are those shown above. This file and the kernels */
/* C it references must exist in your current working directory. */
/* C */
/* CHARACTER*(*) META */
/* PARAMETER ( META = 'spkltc.tm' ) */
/* C */
/* C Use a time step of 1 hour; look up 5 states. */
/* C */
/* DOUBLE PRECISION STEP */
/* PARAMETER ( STEP = 3600.0D0 ) */
/* INTEGER MAXITR */
/* PARAMETER ( MAXITR = 5 ) */
/* C */
/* C Local variables */
/* C */
/* DOUBLE PRECISION DLT */
/* DOUBLE PRECISION ET */
/* DOUBLE PRECISION ET0 */
/* DOUBLE PRECISION LT */
/* DOUBLE PRECISION STATE ( 6 ) */
/* DOUBLE PRECISION STOBS ( 6 ) */
/* INTEGER I */
/* C */
/* C Load the SPK and LSK kernels via the meta-kernel. */
/* C */
/* CALL FURNSH ( META ) */
/* C */
/* C Convert the start time to seconds past J2000 TDB. */
/* C */
/* CALL STR2ET ( '2000 JAN 1 12:00:00 TDB', ET0 ) */
/* C */
/* C Step through a series of epochs, looking up a */
/* C state vector at each one. */
/* C */
/* DO I = 1, MAXITR */
/* ET = ET0 + (I-1)*STEP */
/* C */
/* C Look up a state vector at epoch ET using the */
/* C following inputs: */
/* C */
/* C Target: Moon (NAIF ID code 301) */
/* C Reference frame: J2000 */
/* C Aberration correction: Light time ('LT') */
/* C Observer: Earth (NAIF ID code 399) */
/* C */
/* C Before we can execute this computation, we'll need the */
/* C geometric state of the observer relative to the solar */
/* C system barycenter at ET, expressed relative to the */
/* C J2000 reference frame: */
/* C */
/* CALL SPKSSB ( 399, ET, 'J2000', STOBS ) */
/* C */
/* C Now compute the desired state vector: */
/* C */
/* CALL SPKLTC ( 301, ET, 'J2000', 'LT', */
/* . STOBS, STATE, LT, DLT ) */
/* WRITE (*,*) 'ET = ', ET */
/* WRITE (*,*) 'J2000 x-position (km): ', STATE(1) */
/* WRITE (*,*) 'J2000 y-position (km): ', STATE(2) */
/* WRITE (*,*) 'J2000 z-position (km): ', STATE(3) */
/* WRITE (*,*) 'J2000 x-velocity (km/s): ', STATE(4) */
/* WRITE (*,*) 'J2000 y-velocity (km/s): ', STATE(5) */
/* WRITE (*,*) 'J2000 z-velocity (km/s): ', STATE(6) */
/* WRITE (*,*) 'One-way light time (s): ', LT */
/* WRITE (*,*) 'Light time rate: ', DLT */
/* WRITE (*,*) ' ' */
/* END DO */
/* END */
/* On a PC/Linux/gfortran platform, the following output was */
/* produced: */
/* ET = 0.0000000000000000 */
/* J2000 x-position (km): -291569.26541282982 */
/* J2000 y-position (km): -266709.18647825718 */
/* J2000 z-position (km): -76099.155118763447 */
/* J2000 x-velocity (km/s): 0.64353061322177041 */
/* J2000 y-velocity (km/s): -0.66608181700820079 */
/* J2000 z-velocity (km/s): -0.30132283179625752 */
/* One-way light time (s): 1.3423106103251679 */
/* Light time rate: 1.07316908698977495E-007 */
/* ET = 3600.0000000000000 */
/* J2000 x-position (km): -289240.78128184378 */
/* J2000 y-position (km): -269096.44087958336 */
/* J2000 z-position (km): -77180.899725757539 */
/* J2000 x-velocity (km/s): 0.65006211520087476 */
/* J2000 y-velocity (km/s): -0.66016273921695667 */
/* J2000 z-velocity (km/s): -0.29964267390571342 */
/* One-way light time (s): 1.3426939548635302 */
/* Light time rate: 1.05652598952224259E-007 */
/* ET = 7200.0000000000000 */
/* J2000 x-position (km): -286888.88736709207 */
/* J2000 y-position (km): -271462.30170547962 */
/* J2000 z-position (km): -78256.555682137609 */
/* J2000 x-velocity (km/s): 0.65653599154284592 */
/* J2000 y-velocity (km/s): -0.65419657680401588 */
/* J2000 z-velocity (km/s): -0.29794027307420823 */
/* One-way light time (s): 1.3430713117337547 */
/* Light time rate: 1.03990456898758609E-007 */
/* ET = 10800.000000000000 */
/* J2000 x-position (km): -284513.79173691198 */
/* J2000 y-position (km): -273806.60031034052 */
/* J2000 z-position (km): -79326.043183274567 */
/* J2000 x-velocity (km/s): 0.66295190054599118 */
/* J2000 y-velocity (km/s): -0.64818380709706158 */
/* J2000 z-velocity (km/s): -0.29621577937090349 */
/* One-way light time (s): 1.3434426890693671 */
/* Light time rate: 1.02330665243423737E-007 */
/* ET = 14400.000000000000 */
/* J2000 x-position (km): -282115.70368389413 */
/* J2000 y-position (km): -276129.16976799071 */
/* J2000 z-position (km): -80389.282965712249 */
/* J2000 x-velocity (km/s): 0.66930950377548726 */
/* J2000 y-velocity (km/s): -0.64212490805688027 */
/* J2000 z-velocity (km/s): -0.29446934336246899 */
/* One-way light time (s): 1.3438080956559786 */
/* Light time rate: 1.00673403630050830E-007 */
/* $ Restrictions */
/* 1) The routine SPKGEO should be used instead of this routine */
/* to compute geometric states. SPKGEO introduces less */
/* round-off error when the observer and target have common */
/* center that is closer to both objects than is the solar */
/* system barycenter. */
/* 2) The kernel files to be used by SPKLTC must be loaded */
/* (normally by the SPICELIB kernel loader FURNSH) before */
/* this routine is called. */
/* 3) Unlike most other SPK state computation routines, this */
/* routine requires that the output state be relative to an */
/* inertial reference frame. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Version */
/* - SPICELIB Version 2.0.0, 04-JUL-2014 (NJB) */
/* Discussion of light time corrections was updated. Assertions */
/* that converged light time corrections are unlikely to be */
/* useful were removed. */
/* Last update was 02-MAY-2012 (NJB) */
/* Updated to ensure convergence when CN or XCN light time */
/* corrections are used. The new algorithm also terminates early */
/* (after fewer than three iterations) when convergence is */
/* attained. */
/* Call to ZZPRSCOR was replaced by a call to ZZVALCOR. */
/* - SPICELIB Version 1.0.0, 11-JAN-2008 (NJB) */
/* -& */
/* $ Index_Entries */
/* low-level light time correction */
/* light-time corrected state from spk file */
/* get light-time corrected state */
/* -& */
/* $ Revisions */
/* None. */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* TOL is the tolerance used for a division-by-zero test */
/* performed prior to computation of DLT. */
/* Convergence limit: */
/* Maximum number of light time iterations for any */
/* aberration correction: */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("SPKLTC", (ftnlen)6);
}
if (pass1 || s_cmp(abcorr, prvcor, abcorr_len, (ftnlen)5) != 0) {
/* The aberration correction flag differs from the value it */
/* had on the previous call, if any. Analyze the new flag. */
zzvalcor_(abcorr, attblk, abcorr_len);
if (failed_()) {
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
/* The aberration correction flag is recognized; save it. */
s_copy(prvcor, abcorr, (ftnlen)5, abcorr_len);
/* Set logical flags indicating the attributes of the requested */
/* correction: */
/* XMIT is .TRUE. when the correction is for transmitted */
/* radiation. */
/* USELT is .TRUE. when any type of light time correction */
/* (normal or converged Newtonian) is specified. */
/* USECN indicates converged Newtonian light time correction. */
/* The above definitions are consistent with those used by */
/* ZZVALCOR. */
xmit = attblk[4];
uselt = attblk[1];
usecn = attblk[3];
usestl = attblk[2];
pass1 = FALSE_;
}
/* See if the reference frame is a recognized inertial frame. */
irfnum_(ref, &refid, ref_len);
if (refid == 0) {
setmsg_("The requested frame '#' is not a recognized inertial frame. "
, (ftnlen)60);
errch_("#", ref, (ftnlen)1, ref_len);
sigerr_("SPICE(BADFRAME)", (ftnlen)15);
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
/* Find the geometric state of the target body with respect to */
/* the solar system barycenter. Subtract the state of the */
/* observer to get the relative state. Use this to compute the */
/* one-way light time. */
spkgeo_(targ, et, ref, &c__0, ssbtrg, &ssblt, ref_len);
if (failed_()) {
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
vsubg_(ssbtrg, stobs, &c__6, starg);
dist = vnorm_(starg);
*lt = dist / clight_();
if (*lt == 0.) {
/* This can happen only if the observer and target are at the */
/* same position. We don't consider this an error, but we're not */
/* going to compute the light time derivative. */
*dlt = 0.;
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
if (! uselt) {
/* This is a special case: we're not using light time */
/* corrections, so the derivative */
/* of light time is just */
/* (1/c) * d(VNORM(STARG))/dt */
*dlt = vdot_(starg, &starg[3]) / (dist * clight_());
/* LT and DLT are both set, so we can return. */
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
/* To correct for light time, find the state of the target body */
/* at the current epoch minus the one-way light time. Note that */
/* the observer remains where it is. */
/* Determine the sign of the light time offset. */
if (xmit) {
ltsign = 1;
} else {
ltsign = -1;
}
/* Let NUMITR be the number of iterations we'll perform to */
/* compute the light time. */
if (usecn) {
numitr = 5;
} else {
numitr = 1;
}
i__ = 0;
lterr = 1.;
while(i__ < numitr && lterr > 1e-17) {
/* LT was set either prior to this loop or */
/* during the previous loop iteration. */
epoch = *et + ltsign * *lt;
spkgeo_(targ, &epoch, ref, &c__0, ssbtrg, &ssblt, ref_len);
if (failed_()) {
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
vsubg_(ssbtrg, stobs, &c__6, starg);
prvlt = *lt;
d__1 = vnorm_(starg) / clight_();
*lt = touchd_(&d__1);
/* LTERR is the magnitude of the change between the current */
/* estimate of light time and the previous estimate, relative to */
/* the previous light time corrected epoch. */
/* Computing MAX */
d__3 = 1., d__4 = abs(epoch);
d__2 = (d__1 = *lt - prvlt, abs(d__1)) / max(d__3,d__4);
lterr = touchd_(&d__2);
++i__;
}
/* At this point, STARG contains the light time corrected */
/* state of the target relative to the observer. */
/* Compute the derivative of light time with respect */
/* to time: dLT/dt. Below we derive the formula for */
/* this quantity for the reception case. Let */
/* POBS be the position of the observer relative to the */
/* solar system barycenter. */
/* VOBS be the velocity of the observer relative to the */
/* solar system barycenter. */
/* PTARG be the position of the target relative to the */
/* solar system barycenter. */
/* VTARG be the velocity of the target relative to the */
/* solar system barycenter. */
/* S be the sign of the light time correction. S is */
/* negative for the reception case. */
/* The light-time corrected position of the target relative to */
/* the observer at observation time ET, given the one-way */
/* light time LT is: */
/* PTARG(ET+S*LT) - POBS(ET) */
/* The light-time corrected velocity of the target relative to */
/* the observer at observation time ET is */
/* VTARG(ET+S*LT)*( 1 + S*d(LT)/d(ET) ) - VOBS(ET) */
/* We need to compute dLT/dt. Below, we use the facts that, */
/* for a time-dependent vector X(t), */
/* ||X|| = <X,X> ** (1/2) */
/* d(||X||)/dt = (1/2)<X,X>**(-1/2) * 2 * <X,dX/dt> */
/* = <X,X>**(-1/2) * <X,dX/dt> */
/* = <X,dX/dt> / ||X|| */
/* Newtonian light time equation: */
/* LT = (1/c) * || PTARG(ET+S*LT) - POBS(ET)|| */
/* Differentiate both sides: */
/* dLT/dt = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* * < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT)*(1+S*d(LT)/d(ET)) - VOBS(ET) > */
/* = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* * ( < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT) - VOBS(ET) > */
/* + < PTARG(ET+S*LT) - POBS(ET), */
/* VTARG(ET+S*LT) > * (S*d(LT)/d(ET)) ) */
/* Let */
/* A = (1/c) * ( 1 / || PTARG(ET+S*LT) - POBS(ET) || ) */
/* B = < PTARG(ET+S*LT) - POBS(ET), VTARG(ET+S*LT) - VOBS(ET) > */
/* C = < PTARG(ET+S*LT) - POBS(ET), VTARG(ET+S*LT) > */
/* Then */
/* d(LT)/d(ET) = A * ( B + C * S*d(LT)/d(ET) ) */
/* which implies */
/* d(LT)/d(ET) = A*B / ( 1 - S*C*A ) */
a = 1. / (clight_() * vnorm_(starg));
b = vdot_(starg, &starg[3]);
c__ = vdot_(starg, &ssbtrg[3]);
/* For physically realistic target velocities, S*C*A cannot equal 1. */
/* We'll check for this case anyway. */
if (ltsign * c__ * a > .99999999989999999) {
setmsg_("Target range rate magnitude is approximately the speed of l"
"ight. The light time derivative cannot be computed.", (ftnlen)
110);
sigerr_("SPICE(DIVIDEBYZERO)", (ftnlen)19);
chkout_("SPKLTC", (ftnlen)6);
return 0;
}
/* Compute DLT: the rate of change of light time. */
*dlt = a * b / (1. - ltsign * c__ * a);
/* Overwrite the velocity portion of the output state */
/* with the light-time corrected velocity. */
d__1 = ltsign * *dlt + 1.;
vlcom_(&d__1, &ssbtrg[3], &c_b19, &stobs[3], &starg[3]);
chkout_("SPKLTC", (ftnlen)6);
return 0;
} /* spkltc_ */
/* $Procedure ZZSTELAB ( Private --- stellar aberration correction ) */
/* Subroutine */ int zzstelab_(logical *xmit, doublereal *accobs, doublereal *
vobs, doublereal *starg, doublereal *scorr, doublereal *dscorr)
{
/* System generated locals */
integer i__1;
doublereal d__1, d__2;
/* Builtin functions */
double sqrt(doublereal);
integer s_rnge(char *, integer, char *, integer);
/* Local variables */
extern /* Subroutine */ int vadd_(doublereal *, doublereal *, doublereal *
);
doublereal dphi, rhat[3];
extern /* Subroutine */ int vhat_(doublereal *, doublereal *);
extern doublereal vdot_(doublereal *, doublereal *);
extern /* Subroutine */ int vequ_(doublereal *, doublereal *);
doublereal term1[3], term2[3], term3[3], c__, lcacc[3];
integer i__;
doublereal s;
extern /* Subroutine */ int chkin_(char *, ftnlen);
doublereal saoff[6] /* was [3][2] */, drhat[3];
extern /* Subroutine */ int dvhat_(doublereal *, doublereal *);
doublereal ptarg[3], evobs[3], srhat[6], vphat[3], vtarg[3];
extern /* Subroutine */ int vlcom_(doublereal *, doublereal *, doublereal
*, doublereal *, doublereal *), vperp_(doublereal *, doublereal *,
doublereal *);
extern doublereal vnorm_(doublereal *);
extern logical vzero_(doublereal *);
extern /* Subroutine */ int vlcom3_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *), cleard_(integer *, doublereal *);
doublereal vp[3];
extern doublereal clight_(void);
doublereal dptmag, ptgmag, eptarg[3], dvphat[3], lcvobs[3];
extern /* Subroutine */ int qderiv_(integer *, doublereal *, doublereal *,
doublereal *, doublereal *), sigerr_(char *, ftnlen), chkout_(
char *, ftnlen), setmsg_(char *, ftnlen);
doublereal svphat[6];
extern logical return_(void);
extern /* Subroutine */ int vminus_(doublereal *, doublereal *);
doublereal sgn, dvp[3], svp[6];
/* $ Abstract */
/* SPICE Private routine intended solely for the support of SPICE */
/* routines. Users should not call this routine directly due */
/* to the volatile nature of this routine. */
/* Return the state (position and velocity) of a target body */
/* relative to an observing body, optionally corrected for light */
/* time (planetary aberration) and stellar aberration. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* SPK */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* XMIT I Reception/transmission flag. */
/* ACCOBS I Observer acceleration relative to SSB. */
/* VOBS I Observer velocity relative to to SSB. */
/* STARG I State of target relative to observer. */
/* SCORR O Stellar aberration correction for position. */
/* DSCORR O Stellar aberration correction for velocity. */
/* $ Detailed_Input */
/* XMIT is a logical flag which is set to .TRUE. for the */
/* "transmission" case in which photons *depart* from */
/* the observer's location at an observation epoch ET */
/* and arrive at the target's location at the light-time */
/* corrected epoch ET+LT, where LT is the one-way light */
/* time between observer and target; XMIT is set to */
/* .FALSE. for "reception" case in which photons depart */
/* from the target's location at the light-time */
/* corrected epoch ET-LT and *arrive* at the observer's */
/* location at ET. */
/* Note that the observation epoch is not used in this */
/* routine. */
/* XMIT must be consistent with any light time */
/* corrections used for the input state STARG: if that */
/* state has been corrected for "reception" light time; */
/* XMIT must be .FALSE.; otherwise XMIT must be .TRUE. */
/* ACCOBS is the geometric acceleration of the observer */
/* relative to the solar system barycenter. Units are */
/* km/sec**2. ACCOBS must be expressed relative to */
/* an inertial reference frame. */
/* VOBS is the geometric velocity of the observer relative to */
/* the solar system barycenter. VOBS must be expressed */
/* relative to the same inertial reference frame as */
/* ACCOBS. Units are km/sec. */
/* STARG is the Cartesian state of the target relative to the */
/* observer. Normally STARG has been corrected for */
/* one-way light time, but this is not required. STARG */
/* must be expressed relative to the same inertial */
/* reference frame as ACCOBS. Components are */
/* (x, y, z, dx, dy, dz). Units are km and km/sec. */
/* $ Detailed_Output */
/* SCORR is the stellar aberration correction for the position */
/* component of STARG. Adding SCORR to this position */
/* vector produces the input observer-target position, */
/* corrected for stellar aberration. */
/* The reference frame of SCORR is the common frame */
/* relative to which the inputs ACCOBS, VOBS, and STARG */
/* are expressed. Units are km. */
/* DSCORR is the stellar aberration correction for the velocity */
/* component of STARG. Adding DSCORR to this velocity */
/* vector produces the input observer-target velocity, */
/* corrected for stellar aberration. */
/* The reference frame of DSCORR is the common frame */
/* relative to which the inputs ACCOBS, VOBS, and STARG */
/* are expressed. Units are km/s. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If attempt to divide by zero occurs, the error */
/* SPICE(DIVIDEBYZERO) will be signaled. This case may occur */
/* due to uninitialized inputs. */
/* 2) Loss of precision will occur for geometric cases in which */
/* VOBS is nearly parallel to the position component of STARG. */
/* $ Files */
/* None. */
/* $ Particulars */
/* This routine computes a Newtonian estimate of the stellar */
/* aberration correction of an input state. Normally the input state */
/* has already been corrected for one-way light time. */
/* Since stellar aberration corrections are typically "small" */
/* relative to the magnitude of the input observer-target position */
/* and velocity, this routine avoids loss of precision by returning */
/* the corrections themselves rather than the corrected state */
/* vector. This allows the caller to manipulate (for example, */
/* interpolate) the corrections with greater accuracy. */
/* $ Examples */
/* See SPICELIB routine SPKACS. */
/* $ Restrictions */
/* None. */
/* $ Literature_References */
/* SPK Required Reading. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* $ Version */
/* - SPICELIB Version 2.0.0, 15-APR-2014 (NJB) */
/* Added RETURN test and discovery check-in. */
/* Check for division by zero was added. This */
/* case might occur due to uninitialized inputs. */
/* - SPICELIB Version 1.0.1, 12-FEB-2009 (NJB) */
/* Minor updates were made to the inline documentation. */
/* - SPICELIB Version 1.0.0, 17-JAN-2008 (NJB) */
/* -& */
/* Note for the maintenance programmer */
/* =================================== */
/* The source code of the test utility T_ZZSTLABN must be */
/* kept in sync with the source code of this routine. That */
/* routine uses a value of SEPLIM that forces the numeric */
/* branch of the velocity computation to be taken in all */
/* cases. See the documentation of that routine for details. */
/* SPICELIB functions */
/* Local parameters */
/* Let PHI be the (non-negative) rotation angle of the stellar */
/* aberration correction; then SEPLIM is a limit on how close PHI */
/* may be to zero radians while stellar aberration velocity is */
/* computed analytically. When sin(PHI) is less than SEPLIM, the */
/* velocity must be computed numerically. */
/* Let TDELTA be the time interval, measured in seconds, */
/* used for numerical differentiation of the stellar */
/* aberration correction, when this is necessary. */
/* Local variables */
/* Use discovery check-in. */
if (return_()) {
return 0;
}
/* In the discussion below, the dot product of vectors X and Y */
/* is denoted by */
/* <X,Y> */
/* The speed of light is denoted by the lower case letter "c." BTW, */
/* variable names used here are case-sensitive: upper case "C" */
/* represents a different quantity which is unrelated to the speed */
/* of light. */
/* Variable names ending in "HAT" denote unit vectors. Variable */
/* names starting with "D" denote derivatives with respect to time. */
/* We'll compute the correction SCORR and its derivative with */
/* respect to time DSCORR for the reception case. In the */
/* transmission case, we perform the same computation with the */
/* negatives of the observer velocity and acceleration. */
/* In the code below, we'll store the position and velocity portions */
/* of the input observer-target state STARG in the variables PTARG */
/* and VTARG, respectively. */
/* Let VP be the component of VOBS orthogonal to PTARG. VP */
/* is defined as */
/* VOBS - < VOBS, RHAT > RHAT (1) */
/* where RHAT is the unit vector */
/* PTARG/||PTARG|| */
/* Then */
/* ||VP||/c (2) */
/* is the magnitude of */
/* s = sin( phi ) (3) */
/* where phi is the stellar aberration correction angle. We'll */
/* need the derivative with respect to time of (2). */
/* Differentiating (1) with respect to time yields the */
/* velocity DVP, where, letting */
/* DRHAT = d(RHAT) / dt */
/* VPHAT = VP / ||VP|| */
/* DVPMAG = d( ||VP|| ) / dt */
/* we have */
/* DVP = d(VP)/dt */
/* = ACCOBS - ( ( <VOBS,DRHAT> + <ACCOBS, RHAT> )*RHAT */
/* + <VOBS,RHAT> * DRHAT ) (4) */
/* and */
/* DVPMAG = < DVP, VPHAT > (5) */
/* Now we can find the derivative with respect to time of */
/* the stellar aberration angle phi: */
/* ds/dt = d(sin(phi))/dt = d(phi)/dt * cos(phi) (6) */
/* Using (2) and (5), we have for positive phi, */
/* ds/dt = (1/c)*DVPMAG = (1/c)*<DVP, VPHAT> (7) */
/* Then for positive phi */
/* d(phi)/dt = (1/cos(phi)) * (1/c) * <DVP, VPHAT> (8) */
/* Equation (8) is well-defined as along as VP is non-zero: */
/* if VP is the zero vector, VPHAT is undefined. We'll treat */
/* the singular and near-singular cases separately. */
/* The aberration correction itself is a rotation by angle phi */
/* from RHAT towards VP, so the corrected vector is */
/* ( sin(phi)*VPHAT + cos(phi)*RHAT ) * ||PTARG|| */
/* and we can express the offset of the corrected vector from */
/* PTARG, which is the output SCORR, as */
/* SCORR = */
/* ( sin(phi)*VPHAT + (cos(phi)-1)*RHAT ) * ||PTARG|| (9) */
/* Let DPTMAG be defined as */
/* DPTMAG = d ( ||PTARG|| ) / dt (10) */
/* Then the derivative with respect to time of SCORR is */
/* DSCORR = */
/* ( sin(phi)*DVPHAT */
/* + cos(phi)*d(phi)/dt * VPHAT */
/* + (cos(phi) - 1) * DRHAT */
/* + ( -sin(phi)*d(phi)/dt ) * RHAT ) * ||PTARG|| */
/* + ( sin(phi)*VPHAT + (cos(phi)-1)*RHAT ) * DPTMAG (11) */
/* Computations begin here: */
/* Split STARG into position and velocity components. Compute */
/* RHAT */
/* DRHAT */
/* VP */
/* DPTMAG */
if (*xmit) {
vminus_(vobs, lcvobs);
vminus_(accobs, lcacc);
} else {
vequ_(vobs, lcvobs);
vequ_(accobs, lcacc);
}
vequ_(starg, ptarg);
vequ_(&starg[3], vtarg);
dvhat_(starg, srhat);
vequ_(srhat, rhat);
vequ_(&srhat[3], drhat);
vperp_(lcvobs, rhat, vp);
dptmag = vdot_(vtarg, rhat);
/* Compute sin(phi) and cos(phi), which we'll call S and C */
/* respectively. Note that phi is always close to zero for */
/* realistic inputs (for which ||VOBS|| << CLIGHT), so the */
/* cosine term is positive. */
s = vnorm_(vp) / clight_();
/* Computing MAX */
d__1 = 0., d__2 = 1 - s * s;
c__ = sqrt((max(d__1,d__2)));
if (c__ == 0.) {
/* C will be used as a divisor later (in the computation */
/* of DPHI), so we'll put a stop to the problem here. */
chkin_("ZZSTELAB", (ftnlen)8);
setmsg_("Cosine of the aberration angle is 0; this cannot occur for "
"realistic observer velocities. This case can arise due to un"
"initialized inputs. This cosine value is used as a divisor i"
"n a later computation, so it must not be equal to zero.", (
ftnlen)234);
sigerr_("SPICE(DIVIDEBYZERO)", (ftnlen)19);
chkout_("ZZSTELAB", (ftnlen)8);
return 0;
}
/* Compute the unit vector VPHAT and the stellar */
/* aberration correction. We avoid relying on */
/* VHAT's exception handling for the zero vector. */
if (vzero_(vp)) {
cleard_(&c__3, vphat);
} else {
vhat_(vp, vphat);
}
/* Now we can use equation (9) to obtain the stellar */
/* aberration correction SCORR: */
/* SCORR = */
/* ( sin(phi)*VPHAT + (cos(phi)-1)*RHAT ) * ||PTARG|| */
ptgmag = vnorm_(ptarg);
d__1 = ptgmag * s;
d__2 = ptgmag * (c__ - 1.);
vlcom_(&d__1, vphat, &d__2, rhat, scorr);
/* Now we use S as an estimate of PHI to decide if we're */
/* going to differentiate the stellar aberration correction */
/* analytically or numerically. */
/* Note that S is non-negative by construction, so we don't */
/* need to use the absolute value of S here. */
if (s >= 1e-6) {
/* This is the analytic case. */
/* Compute DVP---the derivative of VP with respect to time. */
/* Recall equation (4): */
/* DVP = d(VP)/dt */
/* = ACCOBS - ( ( <VOBS,DRHAT> + <ACCOBS, RHAT> )*RHAT */
/* + <VOBS,RHAT> * DRHAT ) */
d__1 = -vdot_(lcvobs, drhat) - vdot_(lcacc, rhat);
d__2 = -vdot_(lcvobs, rhat);
vlcom3_(&c_b7, lcacc, &d__1, rhat, &d__2, drhat, dvp);
vhat_(vp, vphat);
/* Now we can compute DVPHAT, the derivative of VPHAT: */
vequ_(vp, svp);
vequ_(dvp, &svp[3]);
dvhat_(svp, svphat);
vequ_(&svphat[3], dvphat);
/* Compute the DPHI, the time derivative of PHI, using equation 8: */
/* d(phi)/dt = (1/cos(phi)) * (1/c) * <DVP, VPHAT> */
dphi = 1. / (c__ * clight_()) * vdot_(dvp, vphat);
/* At long last we've assembled all of the "ingredients" required */
/* to compute DSCORR: */
/* DSCORR = */
/* ( sin(phi)*DVPHAT */
/* + cos(phi)*d(phi)/dt * VPHAT */
/* + (cos(phi) - 1) * DRHAT */
/* + ( -sin(phi)*d(phi)/dt ) * RHAT ) * ||PTARG|| */
/* + ( sin(phi)*VPHAT + (cos(phi)-1)*RHAT ) * DPTMAG */
d__1 = c__ * dphi;
vlcom_(&s, dvphat, &d__1, vphat, term1);
d__1 = c__ - 1.;
d__2 = -s * dphi;
vlcom_(&d__1, drhat, &d__2, rhat, term2);
vadd_(term1, term2, term3);
d__1 = dptmag * s;
d__2 = dptmag * (c__ - 1.);
vlcom3_(&ptgmag, term3, &d__1, vphat, &d__2, rhat, dscorr);
} else {
/* This is the numeric case. We're going to differentiate */
/* the stellar aberration correction offset vector using */
/* a quadratic estimate. */
for (i__ = 1; i__ <= 2; ++i__) {
/* Set the sign of the time offset. */
if (i__ == 1) {
sgn = -1.;
} else {
sgn = 1.;
}
/* Estimate the observer's velocity relative to the */
/* solar system barycenter at the current epoch. We use */
/* the local copies of the input velocity and acceleration */
/* to make a linear estimate. */
d__1 = sgn * 1.;
vlcom_(&c_b7, lcvobs, &d__1, lcacc, evobs);
/* Estimate the observer-target vector. We use the */
/* observer-target state velocity to make a linear estimate. */
d__1 = sgn * 1.;
vlcom_(&c_b7, starg, &d__1, &starg[3], eptarg);
/* Let RHAT be the unit observer-target position. */
/* Compute the component of the observer's velocity */
/* that is perpendicular to the target position; call */
/* this vector VP. Also compute the unit vector in */
/* the direction of VP. */
vhat_(eptarg, rhat);
vperp_(evobs, rhat, vp);
if (vzero_(vp)) {
cleard_(&c__3, vphat);
} else {
vhat_(vp, vphat);
}
/* Compute the sine and cosine of the correction */
/* angle. */
s = vnorm_(vp) / clight_();
/* Computing MAX */
d__1 = 0., d__2 = 1 - s * s;
c__ = sqrt((max(d__1,d__2)));
/* Compute the vector offset of the correction. */
ptgmag = vnorm_(eptarg);
d__1 = ptgmag * s;
d__2 = ptgmag * (c__ - 1.);
vlcom_(&d__1, vphat, &d__2, rhat, &saoff[(i__1 = i__ * 3 - 3) < 6
&& 0 <= i__1 ? i__1 : s_rnge("saoff", i__1, "zzstelab_", (
ftnlen)597)]);
}
/* Now compute the derivative. */
qderiv_(&c__3, saoff, &saoff[3], &c_b7, dscorr);
}
/* At this point the correction offset SCORR and its derivative */
/* with respect to time DSCORR are both set. */
return 0;
} /* zzstelab_ */
