/* $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 SPKAPP ( S/P Kernel, apparent state ) */
/* Subroutine */ int spkapp_(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];
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), spkssb_(
integer *, doublereal *, char *, doublereal *, 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_("SPKAPP", (ftnlen)6);
}
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_("SPKAPP", (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 = 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_("SPKAPP", (ftnlen)6);
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. */
spkssb_(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;
spkssb_(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_("SPKAPP", (ftnlen)6);
return 0;
} /* spkapp_ */
void spkssb_c ( SpiceInt targ,
SpiceDouble et,
ConstSpiceChar * ref,
SpiceDouble starg[6] )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
targ I Target body.
et I Target epoch.
ref I Target reference frame.
starg O State of target.
-Detailed_Input
targ is the standard NAIF ID code for a target body.
et is the epoch (ephemeris time) at which the state 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 CSPICE frame system,
including dynamic and other non-inertial frames.
-Detailed_Output
starg contains the position and velocity of the target body,
relative to the solar system barycenter, at epoch 'et'.
These vectors are rotated into the specified reference
frame. Units are always km and km/sec.
-Parameters
None.
-Exceptions
1) If sufficient information has not been "loaded" via the
routine spklef_c or the PCK kernel loaders, the problem will
be diagnosed by a routine in the call tree of this routine.
2) The error SPICE(EMPTYSTRING) is signaled if the input
string 'ref' does not contain at least one character, since the
input string cannot be converted to a Fortran-style string
in this case.
3) The error SPICE(NULLPOINTER) is signaled if the input string
pointer 'ref' is null.
-Files
See: Restrictions.
-Particulars
In order to compute the state of one body relative to another,
the states of the two bodies must be known relative to a third
body. One simple solution is to use the solar system barycenter
as the third body.
Ephemeris data from more than one segment may be required
to determine the state of a body relative to the barycenter.
spkssb_c reads as many segments as necessary, from as many
files as necessary, using files that have been loaded by
previous calls to spklef_c (load ephemeris file).
-Examples
In the following code fragment, spkssb_c is used to display
the distance from Earth (Body 399) to Mars (body 499) at
a series of epochs.
#include <stdio.h>
#include "SpiceUsr.h"
#define EARTH 399
#define MARS 499
.
.
.
spklef_c ( "DE125.SPK", &handle );
.
.
.
while ( epoch <= end )
{
spkssb_c ( EARTH, epoch, "J2000", searth );
spkssb_c ( MARS, epoch, "J2000", smars );
printf ( "%f %22.15e\n", epoch, vdist_c( searth, smars ) );
epoch += delta;
}
-Restrictions
1) The ephemeris files to be used by spkssb_c must be loaded
by spklef_c before spkssb_c is called.
-Literature_References
NAIF Document 168.0, "S- and P- Kernel (SPK) Specification and
User's Guide"
-Author_and_Institution
N.J. Bachman (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-Version
-CSPICE Version 1.0.2, 20-NOV-2004 (NJB)
Updated description of input argument `ref' to indicate all
frames supported by CSPICE are allowed.
-CSPICE Version 1.0.1, 14-OCT-2003 (EDW)
Various minor corrections to the header.
-CSPICE Version 1.0.0, 23-JUN-1999 (NJB) (WLT) (IMU)
-Index_Entries
state relative to solar system barycenter
-&
*/
{ /* Begin spkssb_c */
/*
Participate in error tracing.
*/
chkin_c ( "spkssb_c" );
/*
Check the input string 'ref' to make sure the pointer
is non-null and the string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "spkssb_c", ref );
spkssb_ ( ( integer * ) &targ,
( doublereal * ) &et,
( char * ) ref,
( doublereal * ) starg,
( ftnlen ) strlen(ref) );
chkout_c ( "spkssb_c" );
} /* End spkssb_c */