/* $Procedure SUBSOL ( Sub-solar point ) */
/* Subroutine */ int subsol_(char *method, char *target, doublereal *et, char
*abcorr, char *obsrvr, doublereal *spoint, ftnlen method_len, ftnlen
target_len, ftnlen abcorr_len, ftnlen obsrvr_len)
{
/* Initialized data */
static doublereal origin[3] = { 0.,0.,0. };
doublereal radii[3];
extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
ftnlen, ftnlen), ltime_(doublereal *, integer *, char *, integer
*, doublereal *, doublereal *, ftnlen);
logical found;
extern logical eqstr_(char *, char *, ftnlen, ftnlen);
doublereal sunlt;
extern /* Subroutine */ int bods2c_(char *, integer *, logical *, ftnlen);
integer obscde;
doublereal lt;
extern /* Subroutine */ int bodvcd_(integer *, char *, integer *, integer
*, doublereal *, ftnlen);
integer frcode;
extern /* Subroutine */ int cidfrm_(integer *, integer *, char *, logical
*, ftnlen);
integer nradii;
char frname[80];
integer trgcde;
doublereal ettarg;
extern /* Subroutine */ int nearpt_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *), sigerr_(
char *, ftnlen), chkout_(char *, ftnlen), setmsg_(char *, ftnlen);
extern logical return_(void);
extern /* Subroutine */ int spkpos_(char *, doublereal *, char *, char *,
char *, doublereal *, doublereal *, ftnlen, ftnlen, ftnlen,
ftnlen), surfpt_(doublereal *, doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, logical *);
doublereal alt, pos[3];
/* $ Abstract */
/* Deprecated: This routine has been superseded by the SPICELIB */
/* routine SUBSLR. This routine is supported for purposes of */
/* backward compatibility only. */
/* Determine the coordinates of the sub-solar point on a target */
/* body as seen by a specified observer at a specified epoch, */
/* optionally corrected for planetary (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 */
/* FRAMES */
/* PCK */
/* SPK */
/* TIME */
/* $ Keywords */
/* GEOMETRY */
/* $ Declarations */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* METHOD I Computation method. */
/* TARGET I Name of target body. */
/* ET I Epoch in ephemeris seconds past J2000 TDB. */
/* ABCORR I Aberration correction. */
/* OBSRVR I Name of observing body. */
/* SPOINT O Sub-solar point on the target body. */
/* $ Detailed_Input */
/* METHOD is a short string specifying the computation method */
/* to be used. The choices are: */
/* 'Near point' The sub-solar point is defined */
/* as the nearest point on the */
/* target to the sun. */
/* 'Intercept' The sub-observer point is */
/* defined as the target surface */
/* intercept of the line */
/* containing the target's center */
/* and the sun's center. */
/* In both cases, the intercept computation treats the */
/* surface of the target body as a triaxial ellipsoid. */
/* The ellipsoid's radii must be available in the kernel */
/* pool. */
/* Neither case nor white space are significant in */
/* METHOD. For example, the string ' NEARPOINT' is */
/* valid. */
/* TARGET is the name of the target body. TARGET is */
/* case-insensitive, and leading and trailing blanks in */
/* TARGET are not significant. Optionally, you may */
/* supply a string containing the integer ID code for */
/* the object. For example both 'MOON' and '301' are */
/* legitimate strings that indicate the moon is the */
/* target body. */
/* This routine assumes that the target body is modeled */
/* by a tri-axial ellipsoid, and that a PCK file */
/* containing its radii has been loaded into the kernel */
/* pool via FURNSH. */
/* ET is the epoch in ephemeris seconds past J2000 at which */
/* the sub-solar point on the target body is to be */
/* computed. */
/* ABCORR indicates the aberration corrections to be applied */
/* when computing the observer-target state. ABCORR */
/* may be any of the following. */
/* 'NONE' Apply no correction. Return the */
/* geometric sub-solar point on the target */
/* body. */
/* 'LT' Correct for planetary (light time) */
/* aberration. Both the state and rotation */
/* of the target body are corrected for one */
/* way light time from target to observer. */
/* The state of the sun relative to the */
/* target is corrected for one way light */
/* from the sun to the target; this state */
/* is evaluated at the epoch obtained by */
/* retarding ET by the one way light time */
/* from target to observer. */
/* 'LT+S' Correct for planetary (light time) and */
/* stellar aberrations. Light time */
/* corrections are the same as in the 'LT' */
/* case above. The target state is */
/* additionally corrected for stellar */
/* aberration as seen by the observer, and */
/* the sun state is corrected for stellar */
/* aberration as seen from the target. */
/* 'CN' Converged Newtonian light time */
/* corrections. This is the same as LT */
/* corrections but with further iterations */
/* to a converged Newtonian light time */
/* solution. Given that relativistic */
/* effects may be as large as the higher */
/* accuracy achieved by this computation, */
/* this is correction is seldom worth the */
/* additional computations required unless */
/* the user incorporates additional */
/* relativistic corrections. Light */
/* time corrections are applied as in the */
/* 'LT' case. */
/* 'CN+S' Converged Newtonian light time */
/* corrections and stellar aberration. */
/* Light time and stellar aberration */
/* corrections are applied as in the */
/* 'LT+S' case. */
/* OBSRVR is the name of the observing body, typically a */
/* spacecraft, the earth, or a surface point on the */
/* earth. OBSRVR is case-insensitive, and leading and */
/* trailing blanks in OBSRVR are not significant. */
/* Optionally, you may supply a string containing the */
/* integer ID code for the object. For example both */
/* 'EARTH' and '399' are legitimate strings that indicate */
/* the earth is the observer. */
/* $ Detailed_Output */
/* SPOINT is the sub-solar point on the target body at ET */
/* expressed relative to the body-fixed frame of the */
/* target body. */
/* The sub-solar point is defined either as the point on */
/* the target body that is closest to the sun, or the */
/* target surface intercept of the line containing the */
/* target's center and the sun's center; the input */
/* argument METHOD selects the definition to be used. */
/* The body-fixed frame, which is time-dependent, is */
/* evaluated at ET if ABCORR is 'NONE'; otherwise the */
/* frame is evaluated at ET-LT, where LT is the one way */
/* light time from target to observer. */
/* The state of the target body is corrected for */
/* aberration as specified by ABCORR; the corrected */
/* state is used in the geometric computation. As */
/* indicated above, the rotation of the target is */
/* retarded by one way light time if ABCORR specifies */
/* that light time correction is to be done. */
/* The state of the sun as seen from the observing */
/* body is also corrected for aberration as specified */
/* by ABCORR. The corrections, when selected, are */
/* applied at the epoch ET-LT, where LT is the one way */
/* light time from target to observer. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* If any of the listed errors occur, the output arguments are */
/* left unchanged. */
/* 1) If the input argument METHOD is not recognized, the error */
/* SPICE(DUBIOUSMETHOD) is signaled. */
/* 2) If either of the input body names TARGET or OBSRVR cannot be */
/* mapped to NAIF integer codes, the error SPICE(IDCODENOTFOUND) */
/* is signaled. */
/* 3) If OBSRVR and TARGET map to the same NAIF integer ID codes, the */
/* error SPICE(BODIESNOTDISTINCT) is signaled. */
/* 4) If frame definition data enabling the evaluation of the state */
/* of the target relative to the observer in target body-fixed */
/* coordinates have not been loaded prior to calling SUBSOL, the */
/* error will be diagnosed and signaled by a routine in the call */
/* tree of this routine. */
/* 5) If the specified aberration correction is not recognized, the */
/* error will be diagnosed and signaled by a routine in the call */
/* tree of this routine. */
/* 6) If insufficient ephemeris data have been loaded prior to */
/* calling SUBSOL, the error will be diagnosed and signaled by a */
/* routine in the call tree of this routine. */
/* 7) If the triaxial radii of the target body have not been loaded */
/* into the kernel pool prior to calling SUBSOL, the error will be */
/* diagnosed and signaled by a routine in the call tree of this */
/* routine. */
/* 8) The target must be an extended body: if any of the radii of */
/* the target body are non-positive, the error will be diagnosed */
/* and signaled by routines in the call tree of this routine. */
/* 9) If PCK data supplying a rotation model for the target body */
/* have not been loaded prior to calling SUBSOL, the error will be */
/* diagnosed and signaled by a routine in the call tree of this */
/* routine. */
/* $ Files */
/* Appropriate SPK, PCK, and frame data must be available to */
/* the calling program before this routine is called. Typically */
/* the data are made available by loading kernels; however the */
/* data may be supplied via subroutine interfaces if applicable. */
/* The following data are required: */
/* - SPK data: ephemeris data for sun, target, and observer must */
/* be loaded. If aberration corrections are used, the states of */
/* sun, target, and observer relative to the solar system */
/* barycenter must be calculable from the available ephemeris */
/* data. Ephemeris data are made available by loading */
/* one or more SPK files via FURNSH. */
/* - PCK data: 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: a rotation model for the target body must */
/* be loaded. This may be provided in a text or binary PCK */
/* file which is loaded via FURNSH. */
/* - Frame data: if a frame definition is required to convert */
/* the sun, 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 */
/* SUBSOL computes the sub-solar point on a target body, as seen by */
/* a specified observer. */
/* There are two different popular ways to define the sub-solar */
/* point: "nearest point on target to the sun" or "target surface */
/* intercept of line containing target and sun." These coincide */
/* when the target is spherical and generally are distinct otherwise. */
/* When comparing sub-point computations with results from sources */
/* other than SPICE, it's essential to make sure the same geometric */
/* definitions are used. */
/* $ Examples */
/* In the following example program, the file MGS.BSP is a */
/* hypothetical binary SPK ephemeris file containing data for the */
/* Mars Global Surveyor orbiter. The SPK file de405s.bsp contains */
/* data for the planet barycenters as well as the Earth, Moon, and */
/* Sun for the time period including the date 1997 Dec 31 12:000 */
/* UTC. MGS0000A.TPC is a planetary constants kernel file */
/* containing radii and rotation model constants. MGS00001.TLS is */
/* a leapseconds file. (File names shown here that are specific */
/* to MGS are not names of actual files.) */
/* IMPLICIT NONE */
/* CHARACTER*25 METHOD ( 2 ) */
/* INTEGER I */
/* DOUBLE PRECISION DPR */
/* DOUBLE PRECISION ET */
/* DOUBLE PRECISION LAT */
/* DOUBLE PRECISION LON */
/* DOUBLE PRECISION RADIUS */
/* DOUBLE PRECISION SPOINT ( 3 ) */
/* DATA METHOD / 'Intercept', 'Near point' / */
/* C */
/* C Load kernel files. */
/* C */
/* CALL FURNSH ( 'MGS00001.TLS' ) */
/* CALL FURNSH ( 'MGS0000A.TPC' ) */
/* CALL FURNSH ( 'de405s.bsp' ) */
/* CALL FURNSH ( 'MGS.BSP' ) */
/* C */
/* C Convert the UTC request time to ET (seconds past */
/* C J2000, TDB). */
/* C */
/* CALL STR2ET ( '1997 Dec 31 12:00:00', ET ) */
/* C */
/* C Compute sub-spacecraft point using light time and stellar */
/* C aberration corrections. Use the "target surface intercept" */
/* C definition of sub-spacecraft point on the first loop */
/* C iteration, and use the "near point" definition on the */
/* C second. */
/* C */
/* DO I = 1, 2 */
/* CALL SUBSOL ( METHOD(I), */
/* . 'MARS', ET, 'LT+S', 'MGS', SPOINT ) */
/* C */
/* C Convert rectangular coordinates to planetocentric */
/* C latitude and longitude. Convert radians to degrees. */
/* C */
/* CALL RECLAT ( SPOINT, RADIUS, LON, LAT ) */
/* LON = LON * DPR () */
/* LAT = LAT * DPR () */
/* C */
/* C Write the results. */
/* C */
/* WRITE (*,*) ' ' */
/* WRITE (*,*) 'Computation method: ', METHOD(I) */
/* WRITE (*,*) ' ' */
/* WRITE (*,*) ' Radius (km) = ', RADIUS */
/* WRITE (*,*) ' Planetocentric Latitude (deg) = ', LAT */
/* WRITE (*,*) ' Planetocentric Longitude (deg) = ', LON */
/* WRITE (*,*) ' ' */
/* END DO */
/* END */
/* $ Restrictions */
/* The appropriate kernel data must have been loaded before this */
/* routine is called. See the Files section above. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* N.J. Bachman (JPL) */
/* J.E. McLean (JPL) */
/* $ Version */
/* - SPICELIB Version 1.2.3, 18-MAY-2010 (BVS) */
/* Index line now states that this routine is deprecated. */
/* - SPICELIB Version 1.2.2, 17-MAR-2009 (EDW) */
/* Typo correction in Required_Reading, changed */
/* FRAME to FRAMES. */
/* - SPICELIB Version 1.2.1, 07-FEB-2008 (NJB) */
/* Abstract now states that this routine is deprecated. */
/* - SPICELIB Version 1.2.0, 24-OCT-2005 (NJB) */
/* Call to BODVAR was replaced with call to BODVCD. */
/* - SPICELIB Version 1.1.0, 22-JUL-2004 (NJB) */
/* Updated to support representations of integers in the input */
/* arguments TARGET and OBSRVR. Deleted references in header to */
/* kernel-specific loaders. Made miscellaneous minor corrections */
/* to header comments. */
/* - SPICELIB Version 1.0.2, 12-DEC-2002 (NJB) */
/* Corrected and updated code example in header. */
/* - SPICELIB Version 1.0.1, 1-NOV-1999 (WLT) */
/* Declared routine LTIME to be external. */
/* - SPICELIB Version 1.0.0, 03-SEP-1999 (NJB) (JEM) */
/* -& */
/* $ Index_Entries */
/* DEPRECATED sub-solar point */
/* -& */
/* $ Revisions */
/* - SPICELIB Version 1.1.0, 22-JUL-2004 (NJB) */
/* Updated to support representations of integers in the */
/* input arguments TARGET and OBSRVR: calls to BODN2C */
/* were replaced by calls to BODS2C. */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("SUBSOL", (ftnlen)6);
}
/* Obtain integer codes for the target and observer. */
bods2c_(target, &trgcde, &found, target_len);
if (! found) {
setmsg_("The target, '#', is not a recognized name for an ephemeris "
"object. The cause of this problem may be that you need an up"
"dated version of the SPICE Toolkit. ", (ftnlen)155);
errch_("#", target, (ftnlen)1, target_len);
sigerr_("SPICE(IDCODENOTFOUND)", (ftnlen)21);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
bods2c_(obsrvr, &obscde, &found, obsrvr_len);
if (! found) {
setmsg_("The observer, '#', is not a recognized name for an ephemeri"
"s object. The cause of this problem may be that you need an "
"updated version of the SPICE Toolkit. ", (ftnlen)157);
errch_("#", obsrvr, (ftnlen)1, obsrvr_len);
sigerr_("SPICE(IDCODENOTFOUND)", (ftnlen)21);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
/* Check the input body codes. If they are equal, signal */
/* an error. */
if (obscde == trgcde) {
setmsg_("In computing the sub-observer point, the observing body and"
" target body are the same. Both are #.", (ftnlen)97);
errch_("#", obsrvr, (ftnlen)1, obsrvr_len);
sigerr_("SPICE(BODIESNOTDISTINCT)", (ftnlen)24);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
/* Get the radii of the target body from the kernel pool. */
bodvcd_(&trgcde, "RADII", &c__3, &nradii, radii, (ftnlen)5);
/* Find the name of the body-fixed frame associated with the */
/* target body. We'll want the state of the target relative to */
/* the observer in this body-fixed frame. */
cidfrm_(&trgcde, &frcode, frname, &found, (ftnlen)80);
if (! found) {
setmsg_("No body-fixed frame is associated with target body #; a fra"
"me kernel must be loaded to make this association. Consult "
"the FRAMES Required Reading for details.", (ftnlen)159);
errch_("#", target, (ftnlen)1, target_len);
sigerr_("SPICE(NOFRAME)", (ftnlen)14);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
/* If we're using aberration corrections, we'll need the */
/* one way light time from the target to the observer. Otherwise, */
/* we set the time time to zero. */
if (eqstr_(abcorr, "NONE", abcorr_len, (ftnlen)4)) {
lt = 0.;
ettarg = *et;
} else {
ltime_(et, &obscde, "<-", &trgcde, &ettarg, <, (ftnlen)2);
}
/* Determine the position of the sun in target body-fixed */
/* coordinates. */
/* Call SPKEZ to compute the position of the sun as seen from the */
/* target body and the light time between them SUNLT. This state is */
/* evaluated at the target epoch ETTARG. We request that the */
/* coordinates of the target-sun position vector POS be returned */
/* relative to the body fixed reference frame associated with the */
/* target body, using aberration corrections specified by the input */
/* argument ABCORR. */
spkpos_("SUN", &ettarg, frname, abcorr, target, pos, &sunlt, (ftnlen)3, (
ftnlen)80, abcorr_len, target_len);
/* Find the sub-solar point using the specified geometric definition. */
if (eqstr_(method, "Near point", method_len, (ftnlen)10)) {
/* Locate the nearest point to the sun on the target. */
nearpt_(pos, radii, &radii[1], &radii[2], spoint, &alt);
} else if (eqstr_(method, "Intercept", method_len, (ftnlen)9)) {
surfpt_(origin, pos, radii, &radii[1], &radii[2], spoint, &found);
/* Since the line in question passes through the center of the */
/* target, there will always be a surface intercept. So we should */
/* never have FOUND = .FALSE. */
if (! found) {
setmsg_("Call to SURFPT returned FOUND=FALSE even though vertex "
"of ray is at target center. This indicates a bug. Please"
" contact NAIF.", (ftnlen)125);
sigerr_("SPICE(BUG)", (ftnlen)10);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
} else {
setmsg_("The computation method # was not recognized. Allowed values"
" are \"Near point\" and \"Intercept.\"", (ftnlen)93);
errch_("#", method, (ftnlen)1, method_len);
sigerr_("SPICE(DUBIOUSMETHOD)", (ftnlen)20);
chkout_("SUBSOL", (ftnlen)6);
return 0;
}
chkout_("SUBSOL", (ftnlen)6);
return 0;
} /* subsol_ */
/* $Procedure RECGEO ( Rectangular to geodetic ) */
/* Subroutine */ int recgeo_(doublereal *rectan, doublereal *re, doublereal *
f, doublereal *long__, doublereal *lat, doublereal *alt)
{
doublereal base[3], a, b, c__;
extern /* Subroutine */ int chkin_(char *, ftnlen), errdp_(char *,
doublereal *, ftnlen), reclat_(doublereal *, doublereal *,
doublereal *, doublereal *);
doublereal radius, normal[3];
extern /* Subroutine */ int nearpt_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *), sigerr_(
char *, ftnlen), chkout_(char *, ftnlen), setmsg_(char *, ftnlen),
surfnm_(doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *);
extern logical return_(void);
/* $ Abstract */
/* Convert from rectangular coordinates to geodetic coordinates. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* None. */
/* $ Keywords */
/* CONVERSION, COORDINATES */
/* $ Declarations */
/* $ Brief_I/O */
/* VARIABLE I/O DESCRIPTION */
/* -------- --- -------------------------------------------------- */
/* RECTAN I Rectangular coordinates of a point. */
/* RE I Equatorial radius of the reference spheroid. */
/* F I Flattening coefficient. */
/* LONG O Geodetic longitude of the point (radians). */
/* LAT O Geodetic latitude of the point (radians). */
/* ALT O Altitude of the point above reference spheroid. */
/* $ Detailed_Input */
/* RECTAN The rectangular coordinates of a point. */
/* RE Equatorial radius of a reference spheroid. This */
/* spheroid is a volume of revolution: its horizontal */
/* cross sections are circular. The shape of the */
/* spheroid is defined by an equatorial radius RE and */
/* a polar radius RP. */
/* F Flattening coefficient = (RE-RP) / RE, where RP is */
/* the polar radius of the spheroid. */
/* $ Detailed_Output */
/* LONG Geodetic longitude of the input point. This is the */
/* angle between the prime meridian and the meridian */
/* containing RECTAN. The direction of increasing */
/* longitude is from the +X axis towards the +Y axis. */
/* LONG is output in radians. The range of LONG is */
/* [-pi, pi]. */
/* LAT Geodetic latitude of the input point. For a point P */
/* on the reference spheroid, this is the angle between */
/* the XY plane and the outward normal vector at P. */
/* For a point P not on the reference spheroid, the */
/* geodetic latitude is that of the closest point to P on */
/* the spheroid. */
/* LAT is output in radians. The range of LAT is */
/* [-pi/2, pi/2]. */
/* ALT Altitude of point above the reference spheroid. */
/* The units associated with ALT are those associated */
/* with the input RECTAN. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* 1) If the equatorial radius is non-positive, the error */
/* SPICE(VALUEOUTOFRANGE) is signaled. */
/* 2) If the flattening coefficient is greater than or equal to */
/* one, the error SPICE(VALUEOUTOFRANGE) is signaled. */
/* 3) For points inside the reference ellipsoid, the nearest */
/* point on the ellipsoid to RECTAN may not be unique, so */
/* latitude may not be well-defined. */
/* $ Files */
/* None. */
/* $ Particulars */
/* Given the body-fixed rectangular coordinates of a point, and the */
/* constants describing the reference spheroid, this routine */
/* returns the geodetic coordinates of the point. The body-fixed */
/* rectangular frame is that having the x-axis pass through the */
/* 0 degree latitude 0 degree longitude point. The y-axis passes */
/* through the 0 degree latitude 90 degree longitude. The z-axis */
/* passes through the 90 degree latitude point. For some bodies */
/* this coordinate system may not be a right-handed coordinate */
/* system. */
/* $ Examples */
/* This routine can be used to convert body fixed rectangular */
/* coordinates (such as the Satellite Tracking and Data Network */
/* of 1973) to geodetic coordinates such as those used by the */
/* United States Geological Survey topographic maps. */
/* The code would look something like this */
/* C */
/* C Shift the STDN-73 coordinates to line up with the center */
/* C of the Clark66 reference system. */
/* C */
/* CALL VSUB ( STDNX, OFFSET, X ) */
/* C */
/* C Using the equatorial radius of the Clark66 spheroid */
/* C (CLARKR = 6378.2064 km) and the Clark 66 flattening */
/* C factor (CLARKF = 1.0D0 / 294.9787D0 ) convert to */
/* C geodetic coordinates of the North American Datum of 1927. */
/* C */
/* CALL RECGEO ( X, CLARKR, CLARKF, LONG, LAT, ALT ) */
/* Below are two tables. */
/* Listed in the first table (under X(1), X(2) and X(3)) are a */
/* number of points whose rectangular coordinates are */
/* taken from the set {-1, 0, 1}. */
/* The results of the code fragment */
/* CALL RECGEO ( X, CLARKR, CLARKF, LONG, LAT, ALT ) */
/* Use the SPICELIB routine CONVRT to convert the angular */
/* quantities to degrees */
/* CALL CONVRT ( LAT, 'RADIANS', 'DEGREES', LAT ) */
/* CALL CONVRT ( LONG, 'RADIANS', 'DEGREES', LONG ) */
/* are listed to 4 decimal places in the second parallel table under */
/* LONG (longitude), LAT (latitude), and ALT (altitude). */
/* X(1) X(2) X(3) LONG LAT ALT */
/* -------------------------- ---------------------------- */
/* 0.0000 0.0000 0.0000 0.0000 90.0000 -6356.5838 */
/* 1.0000 0.0000 0.0000 0.0000 0.0000 -6377.2063 */
/* 0.0000 1.0000 0.0000 90.0000 0.0000 -6377.2063 */
/* 0.0000 0.0000 1.0000 0.0000 90.0000 -6355.5838 */
/* -1.0000 0.0000 0.0000 180.0000 0.0000 -6377.2063 */
/* 0.0000 -1.0000 0.0000 -90.0000 0.0000 -6377.2063 */
/* 0.0000 0.0000 -1.0000 0.0000 -90.0000 -6355.5838 */
/* 1.0000 1.0000 0.0000 45.0000 0.0000 -6376.7921 */
/* 1.0000 0.0000 1.0000 0.0000 88.7070 -6355.5725 */
/* 0.0000 1.0000 1.0000 90.0000 88.7070 -6355.5725 */
/* 1.0000 1.0000 1.0000 45.0000 88.1713 -6355.5612 */
/* $ Restrictions */
/* None. */
/* $ Literature_References */
/* See FUNDAMENTALS OF ASTRODYNAMICS, Bate, Mueller, White */
/* published by Dover for a description of geodetic coordinates. */
/* $ Author_and_Institution */
/* C.H. Acton (JPL) */
/* N.J. Bachman (JPL) */
/* H.A. Neilan (JPL) */
/* W.L. Taber (JPL) */
/* $ Version */
/* - SPICELIB Version 1.0.3, 02-JUL-2007 (NJB) */
/* In Examples section of header, description of right-hand */
/* table was updated to use correct names of columns. Term */
/* "bodyfixed" is now hyphenated. */
/* - SPICELIB Version 1.0.2, 30-JUL-2003 (NJB) (CHA) */
/* Various header changes were made to improve clarity. Some */
/* minor header corrections were made. */
/* - SPICELIB Version 1.0.1, 10-MAR-1992 (WLT) */
/* Comment section for permuted index source lines was added */
/* following the header. */
/* - SPICELIB Version 1.0.0, 31-JAN-1990 (WLT) */
/* -& */
/* $ Index_Entries */
/* rectangular to geodetic */
/* -& */
/* $ Revisions */
/* - Beta Version 3.0.1, 9-JUN-1989 (HAN) */
/* Error handling was added to detect and equatorial radius */
/* whose value is less than or equal to zero. */
/* - Beta Version 2.0.0, 21-DEC-1988 (HAN) */
/* Error handling to detect invalid flattening coefficients */
/* was added. Because the flattening coefficient is used to */
/* compute the length of an axis, it must be checked so that */
/* the length is greater than zero. */
/* -& */
/* SPICELIB functions */
/* Local variables */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("RECGEO", (ftnlen)6);
}
/* The equatorial radius must be positive. If not, signal an error */
/* and check out. */
if (*re <= 0.) {
setmsg_("Equatorial radius was *.", (ftnlen)24);
errdp_("*", re, (ftnlen)1);
sigerr_("SPICE(VALUEOUTOFRANGE)", (ftnlen)22);
chkout_("RECGEO", (ftnlen)6);
return 0;
}
/* If the flattening coefficient is greater than one, the length */
/* of the 'C' axis computed below is negative. If it's equal to one, */
/* the length of the axis is zero. Either case is a problem, so */
/* signal an error and check out. */
if (*f >= 1.) {
setmsg_("Flattening coefficient was *.", (ftnlen)29);
errdp_("*", f, (ftnlen)1);
sigerr_("SPICE(VALUEOUTOFRANGE)", (ftnlen)22);
chkout_("RECGEO", (ftnlen)6);
return 0;
}
/* Determine the lengths of the axes of the reference ellipsoid. */
a = *re;
b = *re;
c__ = *re - *f * *re;
/* Find the point on the reference spheroid closes to the input point */
nearpt_(rectan, &a, &b, &c__, base, alt);
/* From this closest point determine the surface normal */
surfnm_(&a, &b, &c__, base, normal);
/* Using the surface normal, determine the latitude and longitude */
/* of the input point. */
reclat_(normal, &radius, long__, lat);
chkout_("RECGEO", (ftnlen)6);
return 0;
} /* recgeo_ */
/* $Procedure SUBPT ( Sub-observer point ) */
/* Subroutine */ int subpt_(char *method, char *target, doublereal *et, char *
abcorr, char *obsrvr, doublereal *spoint, doublereal *alt, ftnlen
method_len, ftnlen target_len, ftnlen abcorr_len, ftnlen obsrvr_len)
{
/* Initialized data */
static doublereal origin[3] = { 0.,0.,0. };
doublereal radii[3];
extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
ftnlen, ftnlen);
logical found;
extern doublereal vdist_(doublereal *, doublereal *);
extern /* Subroutine */ int spkez_(integer *, doublereal *, char *, char *
, integer *, doublereal *, doublereal *, ftnlen, ftnlen);
extern logical eqstr_(char *, char *, ftnlen, ftnlen);
extern /* Subroutine */ int bods2c_(char *, integer *, logical *, ftnlen);
integer obscde;
doublereal lt;
extern /* Subroutine */ int bodvcd_(integer *, char *, integer *, integer
*, doublereal *, ftnlen);
integer frcode;
extern /* Subroutine */ int cidfrm_(integer *, integer *, char *, logical
*, ftnlen);
integer nradii;
char frname[80];
integer trgcde;
extern /* Subroutine */ int nearpt_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *), sigerr_(
char *, ftnlen), chkout_(char *, ftnlen), setmsg_(char *, ftnlen);
doublereal tstate[6];
extern logical return_(void);
extern /* Subroutine */ int vminus_(doublereal *, doublereal *), surfpt_(
doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *, doublereal *, logical *);
doublereal pos[3];
/* $ Abstract */
/* Deprecated: This routine has been superseded by the SPICELIB */
/* routine SUBPNT. This routine is supported for purposes of */
/* backward compatibility only. */
/* Compute the rectangular coordinates of the sub-observer point on */
/* a target body at a particular epoch, optionally corrected for */
/* planetary (light time) and stellar aberration. Return these */
/* coordinates expressed in the body-fixed frame associated with the */
/* target body. Also, return the observer's altitude above the */
/* target body. */
/* $ Disclaimer */
/* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
/* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
/* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
/* $ Required_Reading */
/* FRAMES */
/* PCK */
/* SPK */
/* TIME */
/* $ Keywords */
/* GEOMETRY */
/* $ Declarations */
/* $ Brief_I/O */
/* Variable I/O Description */
/* -------- --- -------------------------------------------------- */
/* METHOD I Computation method. */
/* TARGET I Name of target body. */
/* ET I Epoch in ephemeris seconds past J2000 TDB. */
/* ABCORR I Aberration correction. */
/* OBSRVR I Name of observing body. */
/* SPOINT O Sub-observer point on the target body. */
/* ALT O Altitude of the observer above the target body. */
/* $ Detailed_Input */
/* METHOD is a short string specifying the computation method */
/* to be used. The choices are: */
/* 'Near point' The sub-observer point is */
/* defined as the nearest point on */
/* the target relative to the */
/* observer. */
/* 'Intercept' The sub-observer point is */
/* defined as the target surface */
/* intercept of the line */
/* containing the observer and the */
/* target's center. */
/* In both cases, the intercept computation treats the */
/* surface of the target body as a triaxial ellipsoid. */
/* The ellipsoid's radii must be available in the kernel */
/* pool. */
/* Neither case nor white space are significant in */
/* METHOD. For example, the string ' NEARPOINT' is */
/* valid. */
/* TARGET is the name of a target body. Optionally, you may */
/* supply the integer ID code for the object as */
/* an integer string. For example both 'MOON' and */
/* '301' are legitimate strings that indicate the */
/* moon is the target body. This routine assumes */
/* that this body is modeled by a tri-axial ellipsoid, */
/* and that a PCK file containing its radii has been */
/* loaded into the kernel pool via FURNSH. */
/* ET is the epoch in ephemeris seconds past J2000 at which */
/* the sub-observer point on the target body is to be */
/* computed. */
/* ABCORR indicates the aberration corrections to be applied */
/* when computing the observer-target state. ABCORR */
/* may be any of the following. */
/* 'NONE' Apply no correction. Return the */
/* geometric sub-observer point on the */
/* target body. */
/* 'LT' Correct for planetary (light time) */
/* aberration. Both the state and rotation */
/* of the target body are corrected for */
/* light time. */
/* 'LT+S' Correct for planetary (light time) and */
/* stellar aberrations. Both the state and */
/* rotation of the target body are */
/* corrected for light time. */
/* 'CN' Converged Newtonian light time */
/* corrections. This is the same as LT */
/* corrections but with further iterations */
/* to a converged Newtonian light time */
/* solution. Given that relativistic */
/* effects may be as large as the higher */
/* accuracy achieved by this computation, */
/* this is correction is seldom worth the */
/* additional computations required unless */
/* the user incorporates additional */
/* relativistic corrections. Both the */
/* state and rotation of the target body */
/* are corrected for light time. */
/* 'CN+S' Converged Newtonian light time */
/* corrections and stellar aberration. */
/* Both the state and rotation of the */
/* target body are corrected for light */
/* time. */
/* OBSRVR is the name of the observing body. This is typically */
/* a spacecraft, the earth, or a surface point on the */
/* earth. Optionally, you may supply the ID code of */
/* the object as an integer string. For example, both */
/* 'EARTH' and '399' are legitimate strings to supply */
/* to indicate the observer is Earth. */
/* $ Detailed_Output */
/* SPOINT is the sub-observer point on the target body at ET */
/* expressed relative to the body-fixed frame of the */
/* target body. */
/* The sub-observer point is defined either as the point */
/* on the target body that is closest to the observer, */
/* or the target surface intercept of the line from the */
/* observer to the target's center; the input argument */
/* METHOD selects the definition to be used. */
/* The body-fixed frame, which is time-dependent, is */
/* evaluated at ET if ABCORR is 'NONE'; otherwise the */
/* frame is evaluated at ET-LT, where LT is the one-way */
/* light time from target to observer. */
/* The state of the target body is corrected for */
/* aberration as specified by ABCORR; the corrected */
/* state is used in the geometric computation. As */
/* indicated above, the rotation of the target is */
/* retarded by one-way light time if ABCORR specifies */
/* that light time correction is to be done. */
/* ALT is the "altitude" of the observer above the target */
/* body. When METHOD specifies a "near point" */
/* computation, ALT is truly altitude in the standard */
/* geometric sense: the length of a segment dropped from */
/* the observer to the target's surface, such that the */
/* segment is perpendicular to the surface at the */
/* contact point SPOINT. */
/* When METHOD specifies an "intercept" computation, ALT */
/* is still the length of the segment from the observer */
/* to the surface point SPOINT, but this segment in */
/* general is not perpendicular to the surface. */
/* $ Parameters */
/* None. */
/* $ Exceptions */
/* If any of the listed errors occur, the output arguments are */
/* left unchanged. */
/* 1) If the input argument METHOD is not recognized, the error */
/* SPICE(DUBIOUSMETHOD) is signaled. */
/* 2) If either of the input body names TARGET or OBSRVR cannot be */
/* mapped to NAIF integer codes, the error SPICE(IDCODENOTFOUND) */
/* is signaled. */
/* 3) If OBSRVR and TARGET map to the same NAIF integer ID codes, the */
/* error SPICE(BODIESNOTDISTINCT) is signaled. */
/* 4) If frame definition data enabling the evaluation of the state */
/* of the target relative to the observer in target body-fixed */
/* coordinates have not been loaded prior to calling SUBPT, the */
/* error will be diagnosed and signaled by a routine in the call */
/* tree of this routine. */
/* 5) If the specified aberration correction is not recognized, the */
/* error will be diagnosed and signaled by a routine in the call */
/* tree of this routine. */
/* 6) If insufficient ephemeris data have been loaded prior to */
/* calling SUBPT, the error will be diagnosed and signaled by a */
/* routine in the call tree of this routine. */
/* 7) If the triaxial radii of the target body have not been loaded */
/* into the kernel pool prior to calling SUBPT, the error will be */
/* diagnosed and signaled by a routine in the call tree of this */
/* routine. */
/* 8) The target must be an extended body: if any of the radii of */
/* the target body are non-positive, the error will be diagnosed */
/* and signaled by routines in the call tree of this routine. */
/* 9) If PCK data supplying a rotation model for the target body */
/* have not been loaded prior to calling SUBPT, the error will be */
/* diagnosed and signaled by a routine in the call tree of this */
/* routine. */
/* $ Files */
/* Appropriate SPK, PCK, and frame kernels must be loaded */
/* prior 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: 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. Either type of file may be loaded via FURNSH. */
/* - 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 */
/* SUBPT computes the sub-observer point on a target body. */
/* (The sub-observer point is commonly called the sub-spacecraft */
/* point when the observer is a spacecraft.) SUBPT also */
/* determines the altitude of the observer above the target body. */
/* There are two different popular ways to define the sub-observer */
/* point: "nearest point on target to observer" or "target surface */
/* intercept of line containing observer and target." These */
/* coincide when the target is spherical and generally are distinct */
/* otherwise. */
/* When comparing sub-point computations with results from sources */
/* other than SPICE, it's essential to make sure the same geometric */
/* definitions are used. */
/* $ Examples */
/* The numerical results shown for this example may differ across */
/* platforms. The results depend on the SPICE kernels used as */
/* input, the compiler and supporting libraries, and the machine */
/* specific arithmetic implementation. */
/* In the following example program, the file */
/* spk_m_031103-040201_030502.bsp */
/* is a binary SPK file containing data for Mars Global Surveyor, */
/* Mars, and the Sun for a time interval bracketing the date */
/* 2004 JAN 1 12:00:00 UTC. */
/* pck00007.tpc is a planetary constants kernel file containing */
/* radii and rotation model constants. naif0007.tls is a */
/* leapseconds kernel. */
/* Find the sub-observer point of the Mars Global Surveyor (MGS) */
/* spacecraft on Mars for a specified time. Perform the computation */
/* twice, using both the "intercept" and "near point" options. */
/* IMPLICIT NONE */
/* CHARACTER*25 METHOD ( 2 ) */
/* INTEGER I */
/* DOUBLE PRECISION ALT */
/* DOUBLE PRECISION DPR */
/* DOUBLE PRECISION ET */
/* DOUBLE PRECISION LAT */
/* DOUBLE PRECISION LON */
/* DOUBLE PRECISION RADIUS */
/* DOUBLE PRECISION SPOINT ( 3 ) */
/* DATA METHOD / 'Intercept', 'Near point' / */
/* C */
/* C Load kernel files. */
/* C */
/* CALL FURNSH ( 'naif0007.tls' ) */
/* CALL FURNSH ( 'pck00007.tpc' ) */
/* CALL FURNSH ( 'spk_m_031103-040201_030502.bsp' ) */
/* C */
/* C Convert the UTC request time to ET (seconds past */
/* C J2000, TDB). */
/* C */
/* CALL STR2ET ( '2004 JAN 1 12:00:00', ET ) */
/* C */
/* C Compute sub-spacecraft point using light time and stellar */
/* C aberration corrections. Use the "target surface intercept" */
/* C definition of sub-spacecraft point on the first loop */
/* C iteration, and use the "near point" definition on the */
/* C second. */
/* C */
/* DO I = 1, 2 */
/* CALL SUBPT ( METHOD(I), */
/* . 'MARS', ET, 'LT+S', */
/* . 'MGS', SPOINT, ALT ) */
/* C */
/* C Convert rectangular coordinates to planetocentric */
/* C latitude and longitude. Convert radians to degrees. */
/* C */
/* CALL RECLAT ( SPOINT, RADIUS, LON, LAT ) */
/* LON = LON * DPR () */
/* LAT = LAT * DPR () */
/* C */
/* C Write the results. */
/* C */
/* WRITE (*,*) ' ' */
/* WRITE (*,*) 'Computation method: ', METHOD(I) */
/* WRITE (*,*) ' ' */
/* WRITE (*,*) ' Radius (km) = ', RADIUS */
/* WRITE (*,*) ' Planetocentric Latitude (deg) = ', LAT */
/* WRITE (*,*) ' Planetocentric Longitude (deg) = ', LON */
/* WRITE (*,*) ' Altitude (km) = ', ALT */
/* WRITE (*,*) ' ' */
/* END DO */
/* END */
/* When this program is executed, the output will be: */
/* Computation method: Intercept */
/* Radius (km) = 3387.97077 */
/* Planetocentric Latitude (deg) = -39.7022724 */
/* Planetocentric Longitude (deg) = -159.226663 */
/* Altitude (km) = 373.173506 */
/* Computation method: Near point */
/* Radius (km) = 3387.9845 */
/* Planetocentric Latitude (deg) = -39.6659329 */
/* Planetocentric Longitude (deg) = -159.226663 */
/* Altitude (km) = 373.166636 */
/* $ Restrictions */
/* None. */
/* $ Literature_References */
/* None. */
/* $ Author_and_Institution */
/* C.H. Acton (JPL) */
/* N.J. Bachman (JPL) */
/* J.E. McLean (JPL) */
/* $ Version */
/* - SPICELIB Version 1.2.3, 18-MAY-2010 (BVS) */
/* Index line now states that this routine is deprecated. */
/* - SPICELIB Version 1.2.2, 17-MAR-2009 (EDW) */
/* Typo correction in Required_Reading, changed */
/* FRAME to FRAMES. */
/* - SPICELIB Version 1.2.1, 07-FEB-2008 (NJB) */
/* Abstract now states that this routine is deprecated. */
/* - SPICELIB Version 1.2.0, 24-OCT-2005 (NJB) */
/* Replaced call to BODVAR with call to BODVCD. */
/* - SPICELIB Version 1.1.0, 21-JUL-2004 (EDW) */
/* Changed BODN2C call to BODS2C giving the routine */
/* the capability to accept string representations of */
/* interger IDs for TARGET and OBSRVR. */
/* - SPICELIB Version 1.0.1, 27-JUL-2003 (NJB) (CHA) */
/* Various header corrections were made. The example program */
/* was upgraded to use real kernels, and the program's output is */
/* shown. */
/* - SPICELIB Version 1.0.0, 03-SEP-1999 (NJB) (JEM) */
/* -& */
/* $ Index_Entries */
/* DEPRECATED sub-observer point */
/* -& */
/* SPICELIB functions */
/* Local parameters */
/* Local variables */
/* Saved variables */
/* Initial values */
/* Standard SPICE error handling. */
if (return_()) {
return 0;
} else {
chkin_("SUBPT", (ftnlen)5);
}
/* Obtain integer codes for the target and observer. */
/* Target... */
bods2c_(target, &trgcde, &found, target_len);
if (! found) {
setmsg_("The target, '#', is not a recognized name for an ephemeris "
"object. The cause of this problem may be that you need an up"
"dated version of the SPICE Toolkit. ", (ftnlen)155);
errch_("#", target, (ftnlen)1, target_len);
sigerr_("SPICE(IDCODENOTFOUND)", (ftnlen)21);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
/* ...observer. */
bods2c_(obsrvr, &obscde, &found, obsrvr_len);
if (! found) {
setmsg_("The observer, '#', is not a recognized name for an ephemeri"
"s object. The cause of this problem may be that you need an "
"updated version of the SPICE Toolkit. ", (ftnlen)157);
errch_("#", obsrvr, (ftnlen)1, obsrvr_len);
sigerr_("SPICE(IDCODENOTFOUND)", (ftnlen)21);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
/* Check the input body codes. If they are equal, signal */
/* an error. */
if (obscde == trgcde) {
setmsg_("In computing the sub-observer point, the observing body and"
" target body are the same. Both are #.", (ftnlen)97);
errch_("#", obsrvr, (ftnlen)1, obsrvr_len);
sigerr_("SPICE(BODIESNOTDISTINCT)", (ftnlen)24);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
/* Get the radii of the target body from the kernel pool. */
bodvcd_(&trgcde, "RADII", &c__3, &nradii, radii, (ftnlen)5);
/* Find the name of the body-fixed frame associated with the */
/* target body. We'll want the state of the target relative to */
/* the observer in this body-fixed frame. */
cidfrm_(&trgcde, &frcode, frname, &found, (ftnlen)80);
if (! found) {
setmsg_("No body-fixed frame is associated with target body #; a fra"
"me kernel must be loaded to make this association. Consult "
"the FRAMES Required Reading for details.", (ftnlen)159);
errch_("#", target, (ftnlen)1, target_len);
sigerr_("SPICE(NOFRAME)", (ftnlen)14);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
/* Determine the position of the observer in target */
/* body-fixed coordinates. */
/* - Call SPKEZR to compute the position of the target */
/* body as seen from the observing body and the light time */
/* (LT) between them. SPKEZR returns a state which is */
/* the position and velocity, but we'll only use the position */
/* which is the first three elements. We request that the */
/* coordinates of POS be returned relative to the body fixed */
/* reference frame associated with the target body, using */
/* aberration corrections specified by the input argument */
/* ABCORR. */
/* - Call VMINUS to negate the direction of the vector (POS) */
/* so it will be the position of the observer as seen from */
/* the target body in target body fixed coordinates. */
/* Note that this result is not the same as the result of */
/* calling SPKEZR with the target and observer switched. We */
/* computed the vector FROM the observer TO the target in */
/* order to get the proper light time and stellar aberration */
/* corrections (if requested). Now we need the inverse of */
/* that corrected vector in order to compute the sub-point. */
spkez_(&trgcde, et, frname, abcorr, &obscde, tstate, <, (ftnlen)80,
abcorr_len);
/* Negate the target's state to obtain the position of the observer */
/* relative to the target. */
vminus_(tstate, pos);
/* Find the sub-point and "altitude" (distance from observer to */
/* sub-point) using the specified geometric definition. */
if (eqstr_(method, "Near point", method_len, (ftnlen)10)) {
/* Locate the nearest point to the observer on the target. */
nearpt_(pos, radii, &radii[1], &radii[2], spoint, alt);
} else if (eqstr_(method, "Intercept", method_len, (ftnlen)9)) {
surfpt_(origin, pos, radii, &radii[1], &radii[2], spoint, &found);
/* Since the line in question passes through the center of the */
/* target, there will always be a surface intercept. So we should */
/* never have FOUND = .FALSE. */
if (! found) {
setmsg_("Call to SURFPT returned FOUND=FALSE even though vertex "
"of ray is at target center. This indicates a bug. Please"
" contact NAIF.", (ftnlen)125);
sigerr_("SPICE(BUG)", (ftnlen)10);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
/* SURFPT doesn't compute altitude, so do it here. */
*alt = vdist_(pos, spoint);
} else {
setmsg_("The computation method # was not recognized. Allowed values"
" are \"Near point\" and \"Intercept.\"", (ftnlen)93);
errch_("#", method, (ftnlen)1, method_len);
sigerr_("SPICE(DUBIOUSMETHOD)", (ftnlen)20);
chkout_("SUBPT", (ftnlen)5);
return 0;
}
chkout_("SUBPT", (ftnlen)5);
return 0;
} /* subpt_ */
