| srfxpt_c |
|
Table of contents
Procedure
srfxpt_c ( Surface intercept point )
void srfxpt_c ( ConstSpiceChar * method,
ConstSpiceChar * target,
SpiceDouble et,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * dref,
ConstSpiceDouble dvec [3],
SpiceDouble spoint [3],
SpiceDouble * dist,
SpiceDouble * trgepc,
SpiceDouble obspos [3],
SpiceBoolean * found )
AbstractDeprecated: This routine has been superseded by the CSPICE routine sincpt_c. This routine is supported for purposes of backward compatibility only. Given an observer and a direction vector defining a ray, compute the surface intercept point of the ray on a target body at a specified epoch, optionally corrected for light time and stellar aberration. Required_ReadingFRAMES NAIF_IDS PCK SPK TIME KeywordsGEOMETRY Brief_I/OVARIABLE 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. dref I Reference frame of input direction vector. dvec I Ray's direction vector. spoint O Surface intercept point on the target body. dist O Distance from the observer to the intercept point. trgepc O Intercept epoch. obspos O Observer position relative to target center. found O Flag indicating whether intercept was found. Detailed_Input
method is a short string providing parameters defining
the computation method to be used. Parameters
include, but are not limited to, the shape model
used to represent the surface of the target body.
The only choice currently supported is
"Ellipsoid" The intercept computation uses
a triaxial ellipsoid to model
the surface of the target body.
The ellipsoid's radii must be
available in the kernel pool.
Neither case nor white space are significant in
`method'. For example, the string " eLLipsoid " is
valid.
In a later Toolkit release, this argument will be
used to invoke a wider range of surface
representations. For example, it will be possible to
represent the target body's surface using a digital
model.
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.
When the target body's surface is represented by a
tri-axial ellipsoid, this routine assumes that a kernel
variable representing the ellipsoid's radii is present
in the kernel pool. Normally the kernel variable would
be defined by loading a PCK file.
et is the epoch of participation of the observer, expressed
as ephemeris seconds past J2000 TDB: `et' is the epoch
at which the observer's state is computed.
When aberration corrections are not used, `et' is also
the epoch at which the state and orientation of the
target body are computed.
When aberration corrections are used, `et' is the epoch
at which the observer's state relative to the solar
system barycenter is computed; in this case the position
and orientation of the target body are computed at et-lt
or et+lt, where `lt' is the one-way light time between
the intercept point and the observer, and the sign
applied to lt depends on the selected correction. See
the description of `abcorr' below for details.
abcorr indicates the aberration correction to be applied
when computing the observer-target state and the
orientation of the target body. `abcorr' may be any of
the following.
"NONE" Apply no correction. Return the
geometric surface intercept point on the
target body.
Let `lt' represent the one-way light time between the
observer and the surface intercept point (note: NOT
between the observer and the target body's center).
The following values of `abcorr' apply to the
"reception" case in which photons depart from the
intercept point'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 location of the surface
intercept point at the moment it
emitted photons arriving at the
observer at `et'.
The light time correction uses an
iterative solution of the light time
equation. The solution invoked by the
"LT" option uses one iteration.
Both the target state as seen by the
observer, and rotation of the target
body, are corrected for light time.
"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
surface intercept point 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. Both the
state and rotation of the target body
are corrected for light time.
"CN+S" Converged Newtonian light time
and stellar aberration corrections.
The following values of `abcorr' apply to the
"transmission" case in which photons *depart* from
the observer's location at `et' and arrive at the
intercept point 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
intercept location at the moment it
receives photons emitted from the
observer's location at `et'.
The light time correction uses an
iterative solution of the light time
equation. The solution invoked by the
"LT" option uses one iteration.
Both the target state as seen by the
observer, and rotation of the target
body, are corrected for light time.
"XLT+S" "Transmission" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation This option modifies the
intercept obtained with the "XLT"
option to account for the observer's
velocity relative to the solar system
barycenter.
"XCN" Converged Newtonian light time
correction. This is the same as "XLT"
correction but with further iterations
to a converged Newtonian light time
solution.
"XCN+S" "Transmission" case: converged
Newtonian light time and stellar
aberration corrections.
obsrvr is the name of the observing body. This is 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.
dref is the name of the reference frame relative to which the
input direction vector is expressed. This may be any
frame supported by the SPICE system, including built-in
frames (documented in the Frames Required Reading) and
frames defined by a loaded frame kernel (FK).
When `dref' designates a non-inertial frame, the
orientation of the frame is evaluated at an epoch
dependent on the frame's center and, if the center is
not the observer, on the selected aberration
correction. See the description of the direction
vector `dvec' for details.
dvec is a pointing vector emanating from the observer. The
intercept with the target body's surface of the ray
defined by the observer and `dvec' is sought.
`dvec' is specified relative to the reference frame
designated by `dref'.
Non-inertial reference frames are treated as follows:
if the center of the frame is at the observer's
location, the frame is evaluated at `et'. If the
frame's center is located elsewhere, then letting
`ltcent' be the one-way light time between the observer
and the central body associated with the frame, the
orientation of the frame is evaluated at et-ltcent,
et+ltcent, or `et' depending on whether the requested
aberration correction is, respectively, for received
radiation, transmitted radiation, or is omitted.
`ltcent' is computed using the method indicated by
`abcorr'.
Detailed_Output
spoint is the surface intercept point on the target body of
the ray defined by the observer and the direction
vector. If the ray intersects the target body in
multiple points, the selected intersection point is
the one closest to the observer. The output
argument `found' (see below) indicates whether an
intercept was found.
`spoint' is expressed in Cartesian coordinates,
relative to the body-fixed frame associated with the
target body. The body-fixed target frame is
evaluated at the intercept epoch `trgepc' (see
description below).
When light time correction is used, the duration of
light travel between `spoint' to the observer is
considered to be the one way light time. When both
light time and stellar aberration corrections are
used, `spoint' is selected such that, when `spoint' is
corrected for light time and the vector from the
observer to the light-time corrected location of
`spoint' is corrected for stellar aberration, the
resulting vector is parallel to the ray defined by
the observer's location and `dvec'.
The components of `spoint' are given in units of km.
dist is the distance between the observer and the surface
intercept on the target body. `dist' is given in units
of km.
trgepc is the "intercept epoch." This is the epoch at which
the ray defined by `obsrvr' and `dvec' intercepts the
target surface at `spoint'. `trgepc' is defined as
follows: letting `lt' be the one-way light time between
the observer and the intercept point, `trgepc' is the
epoch et-lt, et+lt, or `et' depending on whether the
requested aberration correction is, respectively, for
received radiation, transmitted radiation, or
omitted. `lt' is computed using the method indicated by
`abcorr'.
`trgepc' is expressed as seconds past J2000 TDB.
obspos is the vector from the center of the target body at
epoch `trgepc' to the observer at epoch `et'. `obspos' is
expressed in the target body-fixed reference frame
evaluated at `trgepc'. (This is the frame relative to
which `spoint' is given.)
`obspos' is returned to simplify various related
computations that would otherwise be cumbersome. For
example, the vector `xvec' from the observer to `spoint'
can be calculated via the call
vsub_c ( spoint, obspos, xvec );
The components of `obspos' are given in units of km.
found is a logical flag indicating whether or not the ray
intersects the target. If an intersection exists
`found' will be returned as SPICETRUE. If the ray misses
the target, `found' will be returned as SPICEFALSE.
ParametersNone. Exceptions
If any of the listed errors occur, the output arguments are
left unchanged.
1) If the input argument `method' is not recognized, an error
is signaled by a routine in the call tree of this
routine.
2) If `target' cannot be mapped to an ID code, the error
SPICE(IDCODENOTFOUND) is signaled by a routine in the call
tree of this routine.
3) If `obsrvr' cannot be mapped to an ID code, an error is signaled
by a routine in the call tree of this routine.
4) If the input argument `abcorr' is invalid, an error
is signaled by a routine in the call tree of this
routine.
5) If a body-fixed reference frame associated with the target
cannot be found, the error SPICE(NOFRAME) is signaled by a
routine in the call tree of this routine.
6) If `obsrvr' and `target' map to the same NAIF integer ID codes, an
error is signaled by a routine in the call tree of this
routine.
7) 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 srfxpt_c, an
error is signaled by a routine in the call tree of this
routine.
8) If the specified aberration correction is not recognized, an
error is signaled by a routine in the call tree of this
routine.
9) If insufficient ephemeris data have been loaded prior to
calling srfxpt_c, an error is signaled by a
routine in the call tree of this routine. Note that when
light time correction is used, sufficient ephemeris data
must be available to propagate the states of both observer
and target to the solar system barycenter.
10) If the computation method has been specified as "Ellipsoid"
and triaxial radii of the target body have not been loaded
into the kernel pool prior to calling srfxpt_c, an error is
signaled by a routine in the call tree of this routine.
11) If PCK data needed to define the target body-fixed frame have
not been loaded prior to calling srfxpt_c, an error is signaled
by a routine in the call tree of this routine.
12) If the reference frame designated by `dref' is not recognized
by the SPICE frame subsystem, an error is signaled
by a routine in the call tree of this routine.
13) If the direction vector `dvec' is the zero vector, an error
is signaled by a routine in the call tree of this routine.
14) If radii for `target' are not found in the kernel pool, an error
is signaled by a routine in the call tree of this routine.
15) If the size of the `target' body radii kernel variable is not
three, an error is signaled by a routine in the call tree of
this routine.
16) If any of the three `target' body radii is less-than or equal to
zero, an error is signaled by a routine in the call tree of
this routine.
17) If any of the `method', `target', `abcorr', `obsrvr' or `dref'
input string pointers is null, the error SPICE(NULLPOINTER) is
signaled.
18) If any of the `method', `target', `abcorr', `obsrvr' or `dref'
input strings has zero length, the error SPICE(EMPTYSTRING) is
signaled.
Files
Appropriate SPK, PCK, and frame kernels must be loaded by the
calling program before this routine is called. CK, SCLK, and
IK kernels may be required as well.
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_c.
- PCK data: if the computation method is specified as
"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_c.
- 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. Similarly, the frame definition required to map
between the frame designated by `dref' and the target
body-fixed frame must be available. Typically the
definitions of frames not already built-in to SPICE are
supplied by loading a frame kernel.
The following data may be required:
- CK data: if the frame to which `dref' refers is fixed to
a spacecraft instrument or structure, at least one CK file will
be needed to permit transformation of vectors between that
frame and both J2000 and the target body-fixed frame.
- SCLK data: if a CK file is needed, an associated SCLK kernel
is required to enable conversion between encoded SCLK
(used to time-tag CK data) and barycentric dynamical time
(TDB).
- IK data: one or more I-kernels may be required to
enable transformation of vectors from an instrument-fixed
frame to a spacecraft-fixed frame whose attitude is given
by a C-kernel.
In all cases, kernel data are normally loaded once per program
run, NOT every time this routine is called.
ParticularsGiven a ray defined by a direction vector and the location of an observer, srfxpt_c computes the surface intercept point of the ray on a specified target body. srfxpt_c also determines the distance between the observer and the surface intercept point. When aberration corrections are used, this routine finds the value of `spoint' such that, if `spoint' is regarded as an ephemeris object, after the selected aberration corrections are applied to the vector from the observer to `spoint', the resulting vector is parallel to the direction vector `dvec'. This routine computes light time corrections using light time between the observer and the surface intercept point, as opposed to the center of the target. Similarly, stellar aberration corrections done by this routine are based on the direction of the vector from the observer to the light-time corrected intercept point, not to the target center. This technique avoids errors due to the differential between aberration corrections across the target body. Therefore it's valid to use aberration corrections with this routine even when the observer is very close to the intercept point, in particular when the observer-intercept point distance is much less than the observer-target center distance. It's also valid to use stellar aberration corrections even when the intercept point is near or on the limb (as may occur in occultation computations using a point target). When comparing surface intercept 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 these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
1) The following program computes surface intercept points on
Mars for the boresight and FOV boundary vectors of the MGS MOC
narrow angle camera. The intercepts are computed for a single
observation epoch. Light time and stellar aberration
corrections are used. For simplicity, camera distortion is
ignored.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File: srfxpt_ex1.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de405s.bsp Planetary ephemeris
mars_iau2000_v0.tpc Planet orientation and
radii
naif0011.tls Leapseconds
mgs_moc_v20.ti MGS MOC instrument
parameters
mgs_sclkscet_00061.tsc MGS SCLK coefficients
mgs_sc_ext12.bc MGS s/c bus attitude
mgs_ext12_ipng_mgs95j.bsp MGS ephemeris
\begindata
KERNELS_TO_LOAD = ( 'de405s.bsp',
'mars_iau2000_v0.tpc',
'naif0011.tls',
'mgs_moc_v20.ti',
'mgs_sclkscet_00061.tsc',
'mgs_sc_ext12.bc',
'mgs_ext12_ipng_mgs95j.bsp' )
\begintext
End of meta-kernel
Example code begins here.
/.
Program srfxpt_ex1
./
#include <stdio.h>
#include <string.h>
#include "SpiceUsr.h"
#include "SpiceZmc.h"
int main()
{
/.
Local parameters
./
#define ABCLEN 20
#define LNSIZE 81
#define METLEN 41
#define NAMLEN 33
#define TIMLEN 51
#define SHPLEN 81
#define NCORNR 4
/.
Local variables
./
SpiceBoolean found;
SpiceChar * abcorr = "LT+S";
SpiceChar * camera = "MGS_MOC_NA";
SpiceChar dref [NAMLEN];
SpiceChar * method = "Ellipsoid";
SpiceChar * obsrvr = "MGS";
SpiceChar shape [ SHPLEN ];
SpiceChar * target = "Mars";
SpiceChar title [ LNSIZE ];
SpiceChar * utc = "2003 OCT 13 06:00:00 UTC";
SpiceDouble bounds [NCORNR][3];
SpiceDouble bsight [3];
SpiceDouble dist;
SpiceDouble dvec [3];
SpiceDouble et;
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble obspos [3];
SpiceDouble radius;
SpiceDouble spoint [3];
SpiceDouble trgepc;
SpiceInt camid;
SpiceInt i;
SpiceInt n;
/.
Load kernel files:
- Leapseconds kernel
- MGS SCLK kernel
- Text PCK file
- Planetary SPK file
- MGS I-kernel
- MGS spacecraft bus C-kernel
- MGS SPK file
./
furnsh_c ( "srfxpt_ex1.tm" );
/.
Convert the UTC request time to ET (seconds past
J2000, TDB).
./
str2et_c ( utc, &et );
/.
Get the MGS MOC Narrow angle camera (MGS_MOC_NA)
ID code. Then look up the field of view (FOV)
parameters.
./
bodn2c_c ( camera, &camid, &found );
if ( !found )
{
setmsg_c ( "Could not find ID code for "
"instrument #." );
errch_c ( "#", camera );
sigerr_c ( "SPICE(NOTRANSLATION)" );
}
getfov_c ( camid, NCORNR, SHPLEN, NAMLEN,
shape, dref, bsight, &n, bounds );
printf ( "\n"
"Surface Intercept Locations for Camera\n"
"FOV Boundary and Boresight Vectors\n"
"\n"
" Instrument: %s\n"
" Epoch: %s\n"
" Aberration correction: %s\n"
"\n",
camera, utc, abcorr );
/.
Now compute and display the surface intercepts for the
boresight and all of the FOV boundary vectors.
./
for ( i = 0; i <= NCORNR; i++ )
{
if ( i < NCORNR )
{
sprintf ( title, "Corner vector %d", (int)i );
vequ_c ( bounds[i], dvec );
}
else
{
strcpy ( title, "Boresight vector" );
vequ_c ( bsight, dvec );
}
/.
Compute the surface intercept point using
the specified aberration corrections.
srfxpt_c will signal an error if required kernel
data are unavailable. See example (2) below for
a suggestion on detecting absence of C-kernel
data prior to calling srfxpt_c.
./
srfxpt_c ( method,
target, et, abcorr,
obsrvr, dref, dvec,
spoint, &dist, &trgepc, obspos, &found );
if ( found )
{
/.
Convert rectangular coordinates to planetocentric
latitude and longitude. Convert radians to degrees.
./
reclat_c ( spoint, &radius, &lon, &lat );
lon *= dpr_c ();
lat *= dpr_c ();
/.
Display the results.
./
printf ( "\n"
"%s\n", title );
sprintf ( title, " Vector in %s frame = ", dref );
printf ( "\n"
"%s\n", title );
if ( i < NCORNR )
{
printf ( " %18.10e %18.10e %18.10e\n",
bounds[i][0], bounds[i][1], bounds[i][2] );
}
else
{
printf ( " %18.10e %18.10e %18.10e\n",
bsight[0], bsight[1], bsight[2] );
}
printf ( "\n"
" Intercept:\n"
"\n"
" Radius (km) = %18.10e\n"
" Planetocentric Latitude (deg) = %18.10e\n"
" Planetocentric Longitude (deg) = %18.10e\n"
" Range (km) = %18.10e\n"
"\n",
radius, lat, lon, dist );
}
else
{
printf ( "\n"
"Intercept not found.\n"
"\n" );
}
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Surface Intercept Locations for Camera
FOV Boundary and Boresight Vectors
Instrument: MGS_MOC_NA
Epoch: 2003 OCT 13 06:00:00 UTC
Aberration correction: LT+S
Corner vector 0
Vector in MGS_MOC_NA frame =
1.8571383810e-06 -3.8015622659e-03 9.9999277403e-01
Intercept:
Radius (km) = 3.3849411359e+03
Planetocentric Latitude (deg) = -4.8477481852e+01
Planetocentric Longitude (deg) = -1.2347407883e+02
Range (km) = 3.8898310725e+02
Corner vector 1
Vector in MGS_MOC_NA frame =
1.8571383810e-06 3.8015622659e-03 9.9999277403e-01
Intercept:
Radius (km) = 3.3849396988e+03
Planetocentric Latitude (deg) = -4.8481636267e+01
Planetocentric Longitude (deg) = -1.2339882275e+02
Range (km) = 3.8897512490e+02
Corner vector 2
Vector in MGS_MOC_NA frame =
-1.8571383810e-06 3.8015622659e-03 9.9999277403e-01
Intercept:
Radius (km) = 3.3849396899e+03
Planetocentric Latitude (deg) = -4.8481661837e+01
Planetocentric Longitude (deg) = -1.2339882596e+02
Range (km) = 3.8897466598e+02
Corner vector 3
Vector in MGS_MOC_NA frame =
-1.8571383810e-06 -3.8015622659e-03 9.9999277403e-01
Intercept:
Radius (km) = 3.3849411271e+03
Planetocentric Latitude (deg) = -4.8477507428e+01
Planetocentric Longitude (deg) = -1.2347408199e+02
Range (km) = 3.8898264817e+02
Boresight vector
Vector in MGS_MOC_NA frame =
0.0000000000e+00 0.0000000000e+00 1.0000000000e+00
Intercept:
Radius (km) = 3.3849404102e+03
Planetocentric Latitude (deg) = -4.8479579751e+01
Planetocentric Longitude (deg) = -1.2343645375e+02
Range (km) = 3.8897573918e+02
2) srfxpt_c will signal an error if required kernel data are
unavailable: for example, in the program of Example 1, if the
C-kernel containing data for the MGS bus had a gap at epoch `et',
srfxpt_c would be unable to transform the direction vector `dvec'
from the reference frame fixed to the camera to the reference
frame fixed to the target body.
We could modify the code of Example 1 as shown below to test for
the availability of C-kernel data. We would add the declarations
shown, and we'd call the C-kernel reader ckgp_c to find whether the
desired pointing was available. Depending on the value of the
`found' flag returned by ckgp_c, we'd go on to compute the surface
intercept point or respond to the error condition.
.
.
.
/.
Local parameters
./
#define BUSID ( -94000 )
#define MGS ( -94 )
.
.
.
/.
Local variables
./
SpiceDouble clkout;
SpiceDouble cmat [3][3];
SpiceDouble sclkdp;
.
.
.
/.
Look up the transformation from the J2000 frame to the
MGS spacecraft frame. To do this, we'll need to represent
our observation epoch in terms of MGS encoded SCLK.
./
sce2c_c ( MGS, et, &sclkdp );
/.
Look up the spacecraft attitude from the C-kernel.
./
ckgp_c ( BUSID, sclkdp, 0., "J2000",
cmat, &clkout, &found );
if ( found )
{
[Proceed to compute intercept point]
}
else
{
[Handle case where pointing is unavailable
for the epoch of interest]
}
.
.
.
Restrictions
1) A cautionary note: if aberration corrections are used, and if
`dref' is the target body-fixed frame, the epoch at which that
frame is evaluated is offset from `et' by the light time between
the observer and the *center* of the target body. This light
time normally will differ from the light time between the
observer and intercept point. Consequently the orientation of
the target body-fixed frame at `trgepc' will not match that of
the target body-fixed frame at the epoch associated with `dref'.
As a result, various derived quantities may not be as
expected: for example, `obspos' would not be the inverse of the
aberration-corrected position of the target as seen by the
observer.
In many applications the errors arising from this frame
discrepancy may be insignificant; however a safe approach is
to always use as `dref' a frame other than the target body-fixed
frame.
Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) B.V. Semenov (JPL) E.D. Wright (JPL) Version
-CSPICE Version 1.0.5, 01-NOV-2021 (JDR)
Edited the header to comply with NAIF standard.
Updated example #1 to use a meta-kernel to load the required
kernels.
-CSPICE Version 1.0.4, 12-JUL-2016 (EDW)
Edit to example program to use "%d" with explicit casts
to int for printing SpiceInts with printf.
-CSPICE Version 1.0.3, 19-MAY-2010 (BVS)
Index line now states that this routine is deprecated.
-CSPICE Version 1.0.2, 07-FEB-2008 (NJB)
-Abstract now states that this routine is deprecated.
Header typo was corrected; reference to vminus_c was replaced
with reference to vsub_c.
-CSPICE Version 1.0.1, 22-JUL-2004 (NJB)
Made trivial change to description of `obsrvr' in
Detailed Input header section.
-CSPICE Version 1.0.0, 27-FEB-2004 (NJB)
Index_EntriesDEPRECATED surface intercept point |
Fri Dec 31 18:41:13 2021