/* $Procedure ZZSPKZP0 ( S/P Kernel, easy position ) */
/* Subroutine */ int zzspkzp0_(integer *targ, doublereal *et, char *ref, char
*abcorr, integer *obs, doublereal *ptarg, doublereal *lt, ftnlen
ref_len, ftnlen abcorr_len)
{
/* Initialized data */
static logical first = TRUE_;
/* System generated locals */
doublereal d__1;
/* Local variables */
static integer fj2000;
extern /* Subroutine */ int zzrefch0_(integer *, integer *, doublereal *,
doublereal *), zzspkpa0_(integer *, doublereal *, char *,
doublereal *, char *, doublereal *, doublereal *, ftnlen, ftnlen);
static doublereal temp[3], sobs[6];
extern /* Subroutine */ int zzspkgp0_(integer *, doublereal *, char *,
integer *, doublereal *, doublereal *, ftnlen), zzspksb0_(integer
*, doublereal *, char *, doublereal *, ftnlen);
static integer type__;
static logical xmit;
static integer i__;
extern /* Subroutine */ int chkin_(char *, ftnlen);
extern logical eqchr_(char *, char *, ftnlen, ftnlen);
extern /* Subroutine */ int errch_(char *, char *, ftnlen, ftnlen);
static logical found;
extern integer ltrim_(char *, ftnlen);
static doublereal xform[9] /* was [3][3] */;
extern logical eqstr_(char *, char *, ftnlen, ftnlen);
static doublereal postn[3];
extern logical failed_(void);
static integer center;
extern /* Subroutine */ int namfrm_(char *, integer *, ftnlen), frinfo_(
integer *, integer *, integer *, integer *, logical *);
static doublereal ltcent;
extern /* Subroutine */ int sigerr_(char *, ftnlen);
static integer reqfrm, typeid;
extern /* Subroutine */ int chkout_(char *, ftnlen), setmsg_(char *,
ftnlen);
extern logical return_(void);
extern /* Subroutine */ int mxv_(doublereal *, 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 position 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 */
/* NAIF_IDS */
/* FRAMES */
/* TIME */
/* $ Keywords */
/* EPHEMERIS */
/* $ Declarations */
/* $ Abstract */
/* The parameters below form an enumerated list of the recognized */
/* frame types. They are: INERTL, PCK, CK, TK, DYN. The meanings */
/* are outlined below. */
/* $ 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 */
/* INERTL an inertial frame that is listed in the routine */
/* CHGIRF and that requires no external file to */
/* compute the transformation from or to any other */
/* inertial frame. */
/* PCK is a frame that is specified relative to some */
/* INERTL frame and that has an IAU model that */
/* may be retrieved from the PCK system via a call */
/* to the routine TISBOD. */
/* CK is a frame defined by a C-kernel. */
/* TK is a "text kernel" frame. These frames are offset */
/* from their associated "relative" frames by a */
/* constant rotation. */
/* DYN is a "dynamic" frame. These currently are */
/* parameterized, built-in frames where the full frame */
/* definition depends on parameters supplied via a */
/* frame kernel. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* W.L. Taber (JPL) */
/* $ Literature_References */
/* None. */
/* $ Version */
/* - SPICELIB Version 3.0.0, 28-MAY-2004 (NJB) */
/* The parameter DYN was added to support the dynamic frame class. */
/* - SPICELIB Version 2.0.0, 12-DEC-1996 (WLT) */
/* Various unused frames types were removed and the */
/* frame time TK was added. */
/* - SPICELIB Version 1.0.0, 10-DEC-1995 (WLT) */
/* -& */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* TARG I Target body NAIF ID code. */
/* ET I Observer epoch. */
/* REF I Reference frame of output position vector. */
/* ABCORR I Aberration correction flag. */
/* OBS I Observing body NAIF ID code. */
/* PTARG O Position 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 position vector which points */
/* from the observer to the target. */
/* ET is the ephemeris time, expressed as seconds past */
/* J2000 TDB, at which the position of the target body */
/* relative to the observer is to be computed. ET */
/* refers to time at the observer's location. */
/* REF is the name of the reference frame relative to which */
/* the output position vector should be expressed. This */
/* may be any frame supported by the SPICE system, */
/* including built-in frames (documented in the Frames */
/* Required Reading) and frames defined by a loaded */
/* frame kernel (FK). */
/* When REF designates a non-inertial frame, the */
/* orientation of the frame is evaluated at an epoch */
/* dependent on the selected aberration correction. See */
/* the description of the output position vector PTARG */
/* for details. */
/* ABCORR indicates the aberration corrections to be applied to */
/* the position 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 position 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 position of the target at */
/* the moment it emitted photons arriving */
/* at the observer at ET. */
/* The light time correction uses an */
/* 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 */
/* position obtained with the 'LT' option */
/* to account for the observer's velocity */
/* relative to the solar system */
/* barycenter. The result is the apparent */
/* position of the target---the position */
/* 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). */
/* The 'CN' correction typically does not */
/* substantially improve accuracy because */
/* the errors made by ignoring */
/* relativistic effects may be larger than */
/* the improvement afforded by obtaining */
/* convergence of the light time solution. */
/* The 'CN' correction computation also */
/* requires a significantly greater number */
/* of CPU cycles than does the */
/* one-iteration light time correction. */
/* 'CN+S' Converged Newtonian light time */
/* and stellar aberration 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 */
/* position 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 */
/* position 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 position 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 and stellar */
/* aberration corrections. */
/* 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. */
/* OBS is the NAIF ID code for the observing body. */
/* $ Detailed_Output */
/* PTARG is a Cartesian 3-vector representing the position of */
/* the target body relative to the specified observer. */
/* PTARG is corrected for the specified aberrations, and */
/* is expressed with respect to the reference frame */
/* specified by REF. The three components of PTARG */
/* represent the x-, y- and z-components of the target's */
/* position. */
/* PTARG points from the observer's location at ET to */
/* the aberration-corrected location of the target. */
/* Note that the sense of this position vector is */
/* independent of the direction of radiation travel */
/* implied by the aberration correction. */
/* Units are always km. */
/* Non-inertial frames are treated as follows: letting */
/* LTCENT be the one-way light time between the observer */
/* and the central body associated with the frame, the */
/* orientation of the frame is evaluated at ET-LTCENT, */
/* ET+LTCENT, or ET depending on whether the requested */
/* aberration correction is, respectively, for received */
/* radiation, transmitted radiation, or is omitted. */
/* LTCENT is computed using the method indicated by */
/* ABCORR. */
/* LT is the one-way light time between the observer and */
/* target in seconds. If the target position 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 name of target or observer cannot be translated to its */
/* NAIF ID code, the error SPICE(IDCODENOTFOUND) is signaled. */
/* 2) If the reference frame REF is not a recognized reference */
/* frame the error 'SPICE(UNKNOWNFRAME)' is signaled. */
/* 3) If the loaded kernels provide insufficient data to */
/* compute the requested position vector, the deficiency will */
/* be diagnosed by a routine in the call tree of this routine. */
/* 4) If an error occurs while reading an SPK or other kernel file, */
/* the error will be diagnosed by a routine in the call tree */
/* of this routine. */
/* $ Files */
/* This routine computes positions using SPK files that have been */
/* loaded into the SPICE system, normally via the kernel loading */
/* interface routine FURNSH. See the routine FURNSH and the SPK */
/* and KERNEL Required Reading for further information on loading */
/* (and unloading) kernels. */
/* If the output position PTARG is to be expressed relative to a */
/* non-inertial frame, or if any of the ephemeris data used to */
/* compute PTARG 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 position. 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 is part of the user interface to the SPICE ephemeris */
/* system. It allows you to retrieve position information for any */
/* ephemeris object relative to any other in a reference frame that */
/* is convenient for further computations. */
/* Aberration corrections */
/* ====================== */
/* 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. */
/* One-way light time */
/* ------------------ */
/* 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 relative to the solar system barycenter, 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. */
/* Stellar aberration */
/* ------------------ */
/* 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 does not include (the much smaller) */
/* relativistic effects. */
/* 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 also 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. */
/* One may 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': apply both light time and stellar */
/* aberration corrections. */
/* Note that using light time corrections alone ('LT') 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': 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' or 'LT+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 position vector derived directly from */
/* data in an SPK file. */
/* Use 'NONE'. */
/* 5) Use a geometric position vector as a low-accuracy estimate */
/* of the apparent position for an application where execution */
/* speed is critical. */
/* Use 'NONE'. */
/* 6) While this routine cannot perform the relativistic */
/* aberration corrections required to compute positions */
/* with the highest possible accuracy, it can supply the */
/* geometric positions 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 */
/* ============== */
/* ZZSPKZP0 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 position vector is */
/* T(ET) - O(ET) */
/* Reception case */
/* ============== */
/* When any of the options 'LT', 'CN', 'LT+S', 'CN+S' is selected */
/* for ABCORR, ZZSPKZP0 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 */
/* right hand side of the light-time equation (1) yields the */
/* "one-iteration" estimate of the one-way light time ("LT"). */
/* Repeating the process until the estimates of LT converge */
/* yields the "converged Newtonian" light time estimate ("CN"). */
/* 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 light time corrected position vector is */
/* T(ET-LT) - O(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. */
/* Transmission case */
/* ================== */
/* When any of the options 'XLT', 'XCN', 'XLT+S', 'XCN+S' is */
/* selected, ZZSPKZP0 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 light-time corrected position vector is */
/* T(ET+LT) - O(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. */
/* Precision of light time corrections */
/* =================================== */
/* Corrections using one iteration of the light time solution */
/* ---------------------------------------------------------- */
/* When the requested aberration correction is 'LT', 'LT+S', */
/* 'XLT', or 'XLT+S', only one iteration is performed in the */
/* algorithm used to compute LT. */
/* The relative error in this computation */
/* | LT_ACTUAL - LT_COMPUTED | / LT_ACTUAL */
/* is at most */
/* (V/C)**2 */
/* ---------- */
/* 1 - (V/C) */
/* which is well approximated by (V/C)**2, where V is the */
/* velocity of the target relative to an inertial frame and C is */
/* the speed of light. */
/* For nearly all objects in the solar system V is less than 60 */
/* km/sec. The value of C is 300000 km/sec. Thus the one */
/* iteration solution for LT has a potential relative error of */
/* not more than 4*10**-8. This is a potential light time error */
/* of approximately 2*10**-5 seconds per astronomical unit of */
/* distance separating the observer and target. Given the bound */
/* on V cited above: */
/* As long as the observer and target are */
/* separated by less than 50 astronomical units, */
/* the error in the light time returned using */
/* the one-iteration light time corrections */
/* is less than 1 millisecond. */
/* Converged corrections */
/* --------------------- */
/* When the requested aberration correction is 'CN', 'CN+S', */
/* 'XCN', or 'XCN+S', three iterations are performed in the */
/* computation of LT. The relative error present in this */
/* solution is at most */
/* (V/C)**4 */
/* ---------- */
/* 1 - (V/C) */
/* which is well approximated by (V/C)**4. Mathematically the */
/* precision of this computation is better than a nanosecond for */
/* any pair of objects in the solar system. */
/* However, to model the actual light time between target and */
/* observer one must take into account effects due to general */
/* relativity. These may be as high as a few hundredths of a */
/* millisecond for some objects. */
/* When one considers the extra time required to compute the */
/* converged Newtonian light time (the state of the target */
/* relative to the solar system barycenter is looked up three */
/* times instead of once) together with the real gain in */
/* accuracy, it seems unlikely that you will want to request */
/* either the "CN" or "CN+S" light time corrections. However, */
/* these corrections can be useful for testing situations where */
/* high precision (as opposed to accuracy) is required. */
/* Relativistic Corrections */
/* ========================= */
/* This routine does not attempt to perform either general or */
/* special relativistic corrections in computing the various */
/* aberration corrections. For many applications relativistic */
/* corrections are not worth the expense of added computation */
/* cycles. If however, your application requires these additional */
/* corrections we suggest you consult the astronomical almanac (page */
/* B36) for a discussion of how to carry out these corrections. */
/* $ Examples */
/* 1) Load a planetary ephemeris SPK, then look up a series of */
/* geometric positions of the moon relative to the earth, */
/* referenced to the J2000 frame. */
/* IMPLICIT NONE */
/* C */
/* C Local constants */
/* C */
/* CHARACTER*(*) FRAME */
/* PARAMETER ( FRAME = 'J2000' ) */
/* CHARACTER*(*) ABCORR */
/* PARAMETER ( ABCORR = 'NONE' ) */
/* C */
/* C The name of the SPK file shown here is fictitious; */
/* C you must supply the name of an SPK file available */
/* C on your own computer system. */
/* C */
/* CHARACTER*(*) SPK */
/* PARAMETER ( SPK = 'planet.bsp' ) */
/* C */
/* C ET0 represents the date 2000 Jan 1 12:00:00 TDB. */
/* C */
/* DOUBLE PRECISION ET0 */
/* PARAMETER ( ET0 = 0.0D0 ) */
/* C */
/* C Use a time step of 1 hour; look up 100 positions. */
/* C */
/* DOUBLE PRECISION STEP */
/* PARAMETER ( STEP = 3600.0D0 ) */
/* INTEGER MAXITR */
/* PARAMETER ( MAXITR = 100 ) */
/* C */
/* C The NAIF IDs of the earth and moon are 399 and 301 */
/* C respectively. */
/* C */
/* INTEGER OBSRVR */
/* PARAMETER ( OBSRVR = 399 ) */
/* INTEGER TARGET */
/* PARAMETER ( TARGET = 301 ) */
/* C */
/* C Local variables */
/* C */
/* DOUBLE PRECISION ET */
/* DOUBLE PRECISION LT */
/* DOUBLE PRECISION POS ( 3 ) */
/* INTEGER I */
/* C */
/* C Load the SPK file. */
/* C */
/* CALL FURNSH ( SPK ) */
/* C */
/* C Step through a series of epochs, looking up a */
/* C position vector at each one. */
/* C */
/* DO I = 1, MAXITR */
/* ET = ET0 + (I-1)*STEP */
/* CALL ZZSPKZP0 ( TARGET, ET, FRAME, ABCORR, OBSRVR, */
/* . POS, LT ) */
/* WRITE (*,*) 'ET = ', ET */
/* WRITE (*,*) 'J2000 x-position (km): ', POS(1) */
/* WRITE (*,*) 'J2000 y-position (km): ', POS(2) */
/* WRITE (*,*) 'J2000 z-position (km): ', POS(3) */
/* WRITE (*,*) ' ' */
/* END DO */
/* END */
/* $ Restrictions */
/* 1) SPICE Private routine. */
/* $ Literature_References */
/* SPK Required Reading. */
/* $ Author_and_Institution */
/* C.H. Acton (JPL) */
/* B.V. Semenov (JPL) */
/* N.J. Bachman (JPL) */
/* W.L. Taber (JPL) */
/* $ Version */
/* - SPICELIB Version 1.0.0, 05-JAN-2005 (NJB) */
/* Based on SPICELIB Version 3.1.0, 05-JAN-2005 (NJB) */
/* -& */
/* $ Index_Entries */
/* using body names get position relative to an observer */
/* get position relative observer corrected for aberrations */
/* read ephemeris data */
/* read trajectory data */
/* -& */
/* $ Revisions */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("ZZSPKZP0", (ftnlen)8);
}
/* Get the frame id for J2000 on the first call to this routine. */
if (first) {
first = FALSE_;
namfrm_("J2000", &fj2000, (ftnlen)5);
}
/* Decide whether the aberration correction is for received or */
/* transmitted radiation. */
i__ = ltrim_(abcorr, abcorr_len);
xmit = eqchr_(abcorr + (i__ - 1), "X", (ftnlen)1, (ftnlen)1);
/* If we only want geometric positions, then compute just that. */
/* Otherwise, compute the state of the observer relative to */
/* the SSB. Then feed that position into ZZSPKPA0 to compute the */
/* apparent position of the target body relative to the observer */
/* with the requested aberration corrections. */
if (eqstr_(abcorr, "NONE", abcorr_len, (ftnlen)4)) {
zzspkgp0_(targ, et, ref, obs, ptarg, lt, ref_len);
} else {
/* Get the auxiliary information about the requested output */
/* frame. */
namfrm_(ref, &reqfrm, ref_len);
if (reqfrm == 0) {
setmsg_("The requested output frame '#' is not recognized by the"
" reference frame subsystem. Please check that the appro"
"priate kernels have been loaded and that you have correc"
"tly entered the name of the output frame. ", (ftnlen)209);
errch_("#", ref, (ftnlen)1, ref_len);
sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
}
frinfo_(&reqfrm, ¢er, &type__, &typeid, &found);
/* If we are dealing with an inertial frame, we can simply */
/* call ZZSPKSB0, ZZSPKPA0 and return. */
if (type__ == 1) {
zzspksb0_(obs, et, ref, sobs, ref_len);
zzspkpa0_(targ, et, ref, sobs, abcorr, ptarg, lt, ref_len,
abcorr_len);
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
}
/* Still here? */
/* We are dealing with a non-inertial frame. But we need to */
/* do light time and stellar aberration in an inertial frame. */
/* Get the "apparent" position of TARG in the intermediary */
/* inertial reference frame J2000. */
/* We also need the light time to the center of the frame. */
zzspksb0_(obs, et, "J2000", sobs, (ftnlen)5);
zzspkpa0_(targ, et, "J2000", sobs, abcorr, postn, lt, (ftnlen)5,
abcorr_len);
if (failed_()) {
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
}
if (center == *obs) {
ltcent = 0.;
} else if (center == *targ) {
ltcent = *lt;
} else {
zzspkpa0_(¢er, et, "J2000", sobs, abcorr, temp, <cent, (
ftnlen)5, abcorr_len);
}
/* If something went wrong (like we couldn't get the position of */
/* the center relative to the observer) now it is time to quit. */
if (failed_()) {
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
}
/* If the aberration corrections are for transmission, negate */
/* the light time, since we wish to compute the orientation */
/* of the non-inertial frame at an epoch later than ET by */
/* the one-way light time. */
if (xmit) {
ltcent = -ltcent;
}
/* Get the rotation from J2000 to the requested frame */
/* and convert the position. */
d__1 = *et - ltcent;
zzrefch0_(&fj2000, &reqfrm, &d__1, xform);
if (failed_()) {
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
}
mxv_(xform, postn, ptarg);
}
chkout_("ZZSPKZP0", (ftnlen)8);
return 0;
} /* zzspkzp0_ */
/* $Procedure ZZSPKGP0 ( S/P Kernel, geometric position ) */
/* Subroutine */ int zzspkgp0_(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 zzrefch0_(integer *, integer *, doublereal *,
doublereal *), 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 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 */
/* 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. */
/* 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 ZZREFCH0. */
/* 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 */
/* ZZSPKGP0 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. ZZSPKGP0 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). */
/* ZZSPKGP0 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 ZZSPKGP0 ( MOON, ET, 'J2000', EARTH, POS, LT ) */
/* CALL ET2UTC ( ET, 'C', 0, UTC ) */
/* WRITE (*,*) UTC, VNORM ( POS ) */
/* END DO */
/* $ Restrictions */
/* 1) SPICE Private routine. */
/* 2) The ephemeris files to be used by ZZSPKGP0 must be loaded */
/* by SPKLEF before ZZSPKGP0 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 1.1.0, 09-NOV-2005 (NJB) */
/* Updated to remove non-standard use of duplicate arguments */
/* in VADD calls. */
/* - SPICELIB Version 1.0.0, 05-JAN-2005 (NJB) */
/* Based on SPICELIB Version 1.1.0, 05-JAN-2005 (NJB) */
/* -& */
/* $ Index_Entries */
/* geometric position of one body relative to another */
/* -& */
/* $ Revisions */
/* - SPICELIB Version 1.1.0, 09-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_("ZZSPKGP0", (ftnlen)8);
}
/* 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_("ZZSPKGP0", (ftnlen)8);
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 ZZSPKGP0; 2. an uninitialized variable. ", (
ftnlen)215);
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_("ZZSPKGP0", (ftnlen)8);
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,
"zzspkgp0_", (ftnlen)610)] = *targ;
found = TRUE_;
cleard_(&c__6, &starg[(i__1 = i__ * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "zzspkgp0_", (ftnlen)613)]);
while(found && i__ < 20 && ctarg[(i__1 = i__ - 1) < 20 && 0 <= i__1 ?
i__1 : s_rnge("ctarg", i__1, "zzspkgp0_", (ftnlen)615)] != *obs &&
ctarg[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 : s_rnge("ctarg",
i__2, "zzspkgp0_", (ftnlen)615)] != 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, "zzspkgp0_", (ftnlen)624)], 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, "zzspkgp0_", (ftnlen)
634)], &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ?
i__2 : s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)634)], &
ctarg[(i__3 = i__ - 1) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"ctarg", i__3, "zzspkgp0_", (ftnlen)634)]);
/* 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_("ZZSPKGP0", (ftnlen)8);
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 {
zzrefch0_(&tframe[19], &tmpfrm, et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
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_("ZZSPKGP0", (ftnlen)8);
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, "zzspkgp0_", (ftnlen)769)] == cobs) {
ctpos = nct;
cframe = tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "zzspkgp0_", (ftnlen)771)];
} 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 {
zzrefch0_(&cframe, &tmpfrm, et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
return 0;
}
mxv_(psxfrm, sobs, vtemp);
vadd_(vtemp, stemp, sobs);
cframe = tmpfrm;
}
/* Check failed. We don't want to loop */
/* indefinitely. */
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
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_("ZZSPKGP0", (ftnlen)8);
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, "zzspkgp0_", (ftnlen)967)] == tframe[(i__3 = i__) <
20 && 0 <= i__3 ? i__3 : s_rnge("tframe", i__3, "zzspkgp0_", (
ftnlen)967)]) {
vadd_(&starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ? i__2 :
s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)969)], &starg[(
i__3 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__3 ? i__3 :
s_rnge("starg", i__3, "zzspkgp0_", (ftnlen)969)], stemp);
moved_(stemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "zzspkgp0_", (
ftnlen)970)]);
} else if (tframe[(i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"tframe", i__3, "zzspkgp0_", (ftnlen)972)] > 0 && tframe[(
i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge("tframe", i__3,
"zzspkgp0_", (ftnlen)972)] <= 21 && tframe[(i__2 = i__ - 1) <
20 && 0 <= i__2 ? i__2 : s_rnge("tframe", i__2, "zzspkgp0_", (
ftnlen)972)] > 0 && tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2
? i__2 : s_rnge("tframe", i__2, "zzspkgp0_", (ftnlen)972)] <=
21) {
irfrot_(&tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 :
s_rnge("tframe", i__2, "zzspkgp0_", (ftnlen)974)], &
tframe[(i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"tframe", i__3, "zzspkgp0_", (ftnlen)974)], rot);
mxv_(rot, &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ? i__2 :
s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)975)], stemp);
vadd_(stemp, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__2
? i__2 : s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)976)],
vtemp);
moved_(vtemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "zzspkgp0_", (
ftnlen)977)]);
} else {
zzrefch0_(&tframe[(i__2 = i__ - 1) < 20 && 0 <= i__2 ? i__2 :
s_rnge("tframe", i__2, "zzspkgp0_", (ftnlen)981)], &
tframe[(i__3 = i__) < 20 && 0 <= i__3 ? i__3 : s_rnge(
"tframe", i__3, "zzspkgp0_", (ftnlen)981)], et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
return 0;
}
mxv_(psxfrm, &starg[(i__2 = i__ * 6 - 6) < 120 && 0 <= i__2 ?
i__2 : s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)988)],
stemp);
vadd_(stemp, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0 <= i__2
? i__2 : s_rnge("starg", i__2, "zzspkgp0_", (ftnlen)989)],
vtemp);
moved_(vtemp, &c__3, &starg[(i__2 = (i__ + 1) * 6 - 6) < 120 && 0
<= i__2 ? i__2 : s_rnge("starg", i__2, "zzspkgp0_", (
ftnlen)990)]);
}
}
/* 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, "zzspkgp0_", (ftnlen)1003)] == cframe) {
vsub_(&starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "zzspkgp0_", (ftnlen)1005)], sobs, pos);
} else if (tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "zzspkgp0_", (ftnlen)1007)] == 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 {
zzrefch0_(&cframe, &refid, et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
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, "zzspkgp0_", (ftnlen)1038)], stemp, pos)
;
} else if (cframe > 0 && cframe <= 21 && tframe[(i__1 = ctpos - 1) < 20 &&
0 <= i__1 ? i__1 : s_rnge("tframe", i__1, "zzspkgp0_", (ftnlen)
1041)] > 0 && tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 :
s_rnge("tframe", i__1, "zzspkgp0_", (ftnlen)1041)] <= 21) {
/* If both frames are inertial we use IRFROT instead of */
/* ZZREFCH0 to get things into a common frame. */
irfrot_(&tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 : s_rnge(
"tframe", i__1, "zzspkgp0_", (ftnlen)1047)], &cframe, rot);
mxv_(rot, &starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "zzspkgp0_", (ftnlen)1048)], stemp);
vsub_(stemp, sobs, pos);
} else {
/* Use the more general routine ZZREFCH0 to make the */
/* transformation. */
zzrefch0_(&tframe[(i__1 = ctpos - 1) < 20 && 0 <= i__1 ? i__1 :
s_rnge("tframe", i__1, "zzspkgp0_", (ftnlen)1056)], &cframe,
et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
return 0;
}
mxv_(psxfrm, &starg[(i__1 = ctpos * 6 - 6) < 120 && 0 <= i__1 ? i__1 :
s_rnge("starg", i__1, "zzspkgp0_", (ftnlen)1063)], 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 {
zzrefch0_(&cframe, &refid, et, psxfrm);
if (failed_()) {
chkout_("ZZSPKGP0", (ftnlen)8);
return 0;
}
mxv_(psxfrm, pos, stemp);
moved_(stemp, &c__3, pos);
}
*lt = vnorm_(pos) / clight_();
chkout_("ZZSPKGP0", (ftnlen)8);
return 0;
} /* zzspkgp0_ */
