void gfdist_c ( ConstSpiceChar * target,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
Return the time window over which a specified constraint on
observer-target distance is met.
GF
NAIF_IDS
SPK
TIME
WINDOWS
EPHEMERIS
EVENT
GEOMETRY
SEARCH
WINDOW
Variable I/O Description
--------------- --- ------------------------------------------------
SPICE_GF_CNVTOL P Convergence tolerance
target I Name of the target body.
abcorr I Aberration correction flag.
obsrvr I Name of the observing body.
relate I Relational operator.
refval I Reference value.
adjust I Adjustment value for absolute extrema searches.
step I Step size used for locating extrema and roots.
nintvls I Workspace window interval count.
cnfine I-O SPICE window to which the search is confined.
result O SPICE window containing results.
target is the name of a target body. 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.
The target and observer define a position vector which
points from the observer to the target; the length of
this vector is the "distance" that serves as the subject
of the search performed by this routine.
Case and leading or trailing blanks are not significant
in the string `target'.
abcorr indicates the aberration corrections to be applied to
the observer-target position vector to account for
one-way light time and stellar aberration.
Any aberration correction accepted by the SPICE
routine spkezr_c is accepted here. See the header
of spkezr_c for a detailed description of the
aberration correction options. For convenience,
the options are listed below:
"NONE" Apply no correction.
"LT" "Reception" case: correct for
one-way light time using a Newtonian
formulation.
"LT+S" "Reception" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
"CN" "Reception" case: converged
Newtonian light time correction.
"CN+S" "Reception" case: converged
Newtonian light time and stellar
aberration corrections.
"XLT" "Transmission" case: correct for
one-way light time using a Newtonian
formulation.
"XLT+S" "Transmission" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
"XCN" "Transmission" case: converged
Newtonian light time correction.
"XCN+S" "Transmission" case: converged
Newtonian light time and stellar
aberration corrections.
Case and leading or trailing blanks are not significant
in the string `abcorr'.
obsrvr is the name of the observing body. 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 observer.
Case and leading or trailing blanks are not significant
in the string `obsrvr'.
relate is a relational operator used to define a constraint on
the observer-target distance. The result window found by
this routine indicates the time intervals where the
constraint is satisfied. Supported values of `relate'
and corresponding meanings are shown below:
">" Distance is greater than the reference
value `refval'.
"=" Distance is equal to the reference
value `refval'.
"<" Distance is less than the reference
value `refval'.
"ABSMAX" Distance is at an absolute maximum.
"ABSMIN" Distance is at an absolute minimum.
"LOCMAX" Distance is at a local maximum.
"LOCMIN" Distance is at a local minimum.
`relate' may be used to specify an "adjusted" absolute
extremum constraint: this requires the distance
to be within a specified offset relative to an
absolute extremum. The argument `adjust' (described
below) is used to specify this offset.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
Case and leading or trailing blanks are not significant
in the string `relate'.
`refval' is the reference value used together with the argument
`relate' to define an equality or inequality to be
satisfied by the distance between the specified target
and observer. See the discussion of `relate' above for
further information.
The units of `refval' are km.
adjust is a parameter used to modify searches for absolute
extrema: when `relate' is set to "ABSMAX" or "ABSMIN"
and `adjust' is set to a positive value, gfdist_c will
find times when the observer-target distance is within
`adjust' km of the specified extreme value.
If `adjust' is non-zero and a search for an absolute
minimum `min' is performed, the result window contains
time intervals when the observer-target distance has
values between `min' and min+adjust.
If the search is for an absolute maximum `max', the
corresponding range is from max-adjust to `max'.
`adjust' is not used for searches for local extrema,
equality or inequality conditions.
step is the step size to be used in the search. `step' must
be shorter than any maximal time interval on which the
specified distance function is monotone increasing or
decreasing. That is, if the confinement window is
partitioned into alternating intervals on which the
distance function is either monotone increasing or
decreasing, `step' must be shorter than any of these
intervals.
However, `step' must not be *too* short, or the search
will take an unreasonable amount of time.
The choice of `step' affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
See the discussion of the parameter SPICE_GF_CNVTOL for
details.
STEP has units of TDB seconds.
nintvls is a parameter specifying the number of intervals that
can be accommodated by each of the dynamically allocated
workspace windows used internally by this routine.
In many cases, it's not necessary to compute an accurate
estimate of how many intervals are needed; rather, the
user can pick a size considerably larger than what's
really required.
However, since excessively large arrays can prevent
applications from compiling, linking, or running
properly, sometimes `nintvls' must be set according to
the actual workspace requirement. A rule of thumb for
the number of intervals needed is
nintvls = 2*n + ( m / step )
where
n is the number of intervals in the confinement
window
m is the measure of the confinement window, in
units of seconds
step is the search step size in seconds
cnfine is a SPICE window that confines the time period over
which the specified search is conducted. `cnfine' may
consist of a single interval or a collection of
intervals.
The endpoints of the time intervals comprising `cnfine'
are interpreted as seconds past J2000 TDB.
See the Examples section below for a code example that
shows how to create a confinement window.
cnfine is the input confinement window, updated if necessary so
the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result is the window of intervals, contained within the
confinement window `cnfine', on which the specified
distance constraint is satisfied.
The endpoints of the time intervals comprising `result'
are interpreted as seconds past J2000 TDB.
If `result' is non-empty on input, its contents will be
discarded before gfdist_c conducts its search.
SPICE_GF_CNVTOL
is the convergence tolerance used for finding endpoints
of the intervals comprising the result window.
SPICE_GF_CNVTOL is used to determine when binary
searches for roots should terminate: when a root is
bracketed within an interval of length SPICE_GF_CNVTOL,
the root is considered to have been found.
The accuracy, as opposed to precision, of roots found by
this routine depends on the accuracy of the input data.
In most cases, the accuracy of solutions will be
inferior to their precision.
SPICE_GF_CNVTOL is declared in the header file
SpiceGF.h.
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
6) If `adjust' is negative, an error is signaled by a routine in
the call tree of this routine.
7) If either of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
8) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
9) If the workspace interval count is less than 1, the error
SPICE(VALUEOUTOFRANGE) will be signaled.
10) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
11) If the output SPICE window `result' has insufficient capacity to
contain the number of intervals on which the specified distance
condition is met, the error will be diagnosed by a routine in
the call tree of this routine. If the result window has size
less than 2, the error SPICE(INVALIDDIMENSION) will be signaled
by this routine.
12) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
13) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
14) If either input cell has type other than SpiceDouble,
the error SPICE(TYPEMISMATCH) is signaled.
Appropriate SPICE 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 for the
time period defined by the confinement window 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.
- If non-inertial reference frames are used by the SPK files,
then PCK files, frame kernels, C-kernels, and SCLK kernels may
be needed.
Kernel data are normally loaded once per program run, NOT every time
this routine is called.
This routine determines a set of one or more time intervals
within the confinement window when the distance between the
specified target and observer satisfies a caller-specified
constraint. The resulting set of intervals is returned as a SPICE
window.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
distance function is monotone increasing and monotone decreasing.
Each of these time periods is represented by a SPICE window. Having
found these windows, all of the distance function's local extrema
within the confinement window are known. Absolute extrema then can
be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. With these solutions
in hand, solutions of inequalities are easily found as well.
Step Size
=========
The monotone windows (described above) are found via a two-step
search process. Each interval of the confinement window is searched
as follows: first, the input step size is the time separation at
which the sign of the rate of change of distance ("range rate") is
sampled. Starting at the left endpoint of the interval, samples will
be taken at each step. If a change of sign is found, a root has been
bracketed; at that point, the time at which the range rate is zero
can be found by a refinement process, for example, via binary
search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the distance function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is longer than the
shortest solution interval.
Having some knowledge of the relative geometry of the target and
observer can be a valuable aid in picking a reasonable step size.
In general, the user can compensate for lack of such knowledge by
picking a very short step size; the cost is increased computation
time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process to
locate them. "Roots" include times when extrema are attained and
times when the distance function is equal to a reference value or
adjusted extremum. All endpoints of the intervals comprising the
result window are either endpoints of intervals of the confinement
window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set via the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
tolerance doesn't limit the accuracy of solutions found by this
routine. In general the accuracy of input data will be the limiting
factor.
The user may change the convergence tolerance from the default
SPICE_GF_CNVTOL value by calling the routine gfstol_c, e.g.
gfstol_c( tolerance value )
Call gfstol_c prior to calling this routine. All subsequent
searches will use the updated tolerance value.
To use a different tolerance value, a lower-level GF routine such
as gfevnt_c must be called. Making the tolerance tighter than
SPICE_GF_CNVTOL is unlikely to be useful, since the results are unlikely
to be more accurate. Making the tolerance looser will speed up
searches somewhat, since a few convergence steps will be omitted.
However, in most cases, the step size is likely to have a much
greater affect on processing time than would the convergence
tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed. See the "CASCADE"
example program in gf.req for a demonstration.
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) Find times during the first three months of the year 2007
when the Earth-Moon distance is greater than 400000 km.
Display the start and stop times of the time intervals
over which this constraint is met, along with the Earth-Moon
distance at each interval endpoint.
We expect the Earth-Moon distance to be an oscillatory function
with extrema roughly two weeks apart. Using a step size of one
day will guarantee that the GF system will find all distance
extrema. (Recall that a search for distance extrema is an
intermediate step in the GF search process.)
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: standard.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
--------- --------
de421.bsp Planetary ephemeris
pck00008.tpc Planet orientation and
radii
naif0009.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00008.tpc',
'naif0009.tls' )
\begintext
End of meta-kernel
Example code begins here.
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Constants
./
#define TIMFMT "YYYY MON DD HR:MN:SC.###"
#define MAXWIN 200
#define NINTVL 100
#define TIMLEN 41
/.
Local variables
./
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SPICEDOUBLE_CELL ( cnfine, MAXWIN );
SPICEDOUBLE_CELL ( result, MAXWIN );
SpiceDouble adjust;
SpiceDouble dist;
SpiceDouble et0;
SpiceDouble et1;
SpiceDouble lt;
SpiceDouble pos [3];
SpiceDouble refval;
SpiceDouble start;
SpiceDouble step;
SpiceDouble stop;
SpiceInt i;
/.
Load kernels.
./
furnsh_c ( "standard.tm" );
/.
Store the time bounds of our search interval in
the confinement window.
./
str2et_c ( "2007 JAN 1", &et0 );
str2et_c ( "2007 APR 1", &et1 );
wninsd_c ( et0, et1, &cnfine );
/.
Search using a step size of 1 day (in units of
seconds). The reference value is 400000 km.
We're not using the adjustment feature, so
we set `adjust' to zero.
./
step = spd_c();
refval = 4.e5;
adjust = 0.0;
/.
Perform the search. The set of times when the
constraint is met will be stored in the SPICE
window `result'.
./
gfdist_c ( "MOON", "NONE", "EARTH", ">", refval,
adjust, step, NINTVL, &cnfine, &result );
/.
Display the results.
./
if ( wncard_c(&result) == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < wncard_c(&result); i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result, i, &start, &stop );
/.
Check the distance at the interval's
start and stop times.
./
spkpos_c ( "MOON", start, "J2000", "NONE",
"EARTH", pos, < );
dist = vnorm_c(pos);
timout_c ( start, TIMFMT, TIMLEN, begstr );
printf ( "Start time, distance = %s %17.9f\n",
begstr, dist );
spkpos_c ( "MOON", stop, "J2000", "NONE",
"EARTH", pos, < );
dist = vnorm_c(pos);
timout_c ( stop, TIMFMT, TIMLEN, endstr );
printf ( "Stop time, distance = %s %17.9f\n",
endstr, dist );
}
}
return ( 0 );
}
When this program was executed on a PC/Linux/gcc platform, the
output was:
Start time, distance = 2007 JAN 08 00:10:02.439 399999.999999989
Stop time, distance = 2007 JAN 13 06:36:42.770 400000.000000010
Start time, distance = 2007 FEB 04 07:01:30.094 399999.999999990
Stop time, distance = 2007 FEB 10 09:29:56.659 399999.999999998
Start time, distance = 2007 MAR 03 00:19:19.998 400000.000000006
Stop time, distance = 2007 MAR 10 14:03:33.312 400000.000000007
Start time, distance = 2007 MAR 29 22:52:52.961 399999.999999995
Stop time, distance = 2007 APR 01 00:00:00.000 404531.955232216
Note that the distance at the final solutions interval's stop
time is not close to the reference value of 400000 km. This is
because the interval's stop time was determined by the stop time
of the confinement window.
2) Extend the first example to demonstrate use of all supported
relational operators. Find times when
Earth-Moon distance is = 400000 km
Earth-Moon distance is < 400000 km
Earth-Moon distance is > 400000 km
Earth-Moon distance is at a local minimum
Earth-Moon distance is at a absolute minimum
Earth-Moon distance is > the absolute minimum + 100 km
Earth-Moon distance is at a local maximum
Earth-Moon distance is at a absolute maximum
Earth-Moon distance is > the absolute maximum - 100 km
To shorten the search time and output, use the
shorter search interval
2007 JAN 15 00:00:00 UTC to
2007 MAR 15 00:00:00 UTC
As before, use geometric (uncorrected) positions, so
set the aberration correction flag to 'NONE'.
Use the meta-kernel from the first example.
Example code begins here.
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Constants
./
#define TIMFMT "YYYY MON DD HR:MN:SC.###"
#define LNSIZE 81
#define MAXWIN 200
#define NINTVL 100
#define TIMLEN 41
#define NRELOP 9
/.
Local variables
./
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
static ConstSpiceChar * relate [NRELOP] =
{
"=",
"<",
">",
"LOCMIN",
"ABSMIN",
"ABSMIN",
"LOCMAX",
"ABSMAX",
"ABSMAX"
};
static ConstSpiceChar * templt [NRELOP] =
{
"Condition: distance = # km",
"Condition: distance < # km",
"Condition: distance > # km",
"Condition: distance is a local minimum",
"Condition: distance is the absolute minimum",
"Condition: distance < the absolute minimum + * km",
"Condition: distance is a local maximum",
"Condition: distance is the absolute maximum",
"Condition: distance > the absolute maximum - * km"
};
SpiceChar title [ LNSIZE ];
SPICEDOUBLE_CELL ( cnfine, MAXWIN );
SPICEDOUBLE_CELL ( result, MAXWIN );
static SpiceDouble adjust [NRELOP] =
{
0.0,
0.0,
0.0,
0.0,
0.0,
100.0,
0.0,
0.0,
100.0
};
SpiceDouble dist;
SpiceDouble et0;
SpiceDouble et1;
SpiceDouble lt;
SpiceDouble pos [3];
SpiceDouble refval;
SpiceDouble start;
SpiceDouble step;
SpiceDouble stop;
SpiceInt i;
SpiceInt j;
/.
Load kernels.
./
furnsh_c ( "standard.tm" );
/.
Store the time bounds of our search interval in
the confinement window.
./
str2et_c ( "2007 JAN 15", &et0 );
str2et_c ( "2007 MAR 15", &et1 );
wninsd_c ( et0, et1, &cnfine );
/.
Search using a step size of 1 day (in units of
seconds). Use a reference value of 400000 km.
./
refval = 400000.0;
step = spd_c();
for ( i = 0; i < NRELOP; i++ )
{
gfdist_c ( "MOON", "NONE", "EARTH", relate[i], refval,
adjust[i], step, NINTVL, &cnfine, &result );
/.
Display the results.
./
printf ( "\n" );
/.
Substitute the reference and adjustment values,
where applicable, into the title string:
./
repmd_c ( templt[i], "#", refval, 6, LNSIZE, title );
repmd_c ( title, "*", adjust[i], 6, LNSIZE, title );
printf ( "%s\n", title );
if ( wncard_c(&result) == 0 )
{
printf ( " Result window is empty.\n" );
}
else
{
printf ( " Result window:\n" );
for ( j = 0; j < wncard_c(&result); j++ )
{
/.
Fetch the endpoints of the jth interval
of the result window.
./
wnfetd_c ( &result, j, &start, &stop );
/.
Check the distance at the interval's
start and stop times.
./
spkpos_c ( "MOON", start, "J2000", "NONE",
"EARTH", pos, < );
dist = vnorm_c(pos);
timout_c ( start, TIMFMT, TIMLEN, begstr );
printf ( " Start time, distance = %s %17.9f\n",
begstr, dist );
spkpos_c ( "MOON", stop, "J2000", "NONE",
"EARTH", pos, < );
dist = vnorm_c(pos);
timout_c ( stop, TIMFMT, TIMLEN, endstr );
printf ( " Stop time, distance = %s %17.9f\n",
endstr, dist );
}
}
}
printf ( "\n" );
return ( 0 );
}
When this program was executed on a PC/Linux/gcc platform, the
output was:
Condition: distance = 4.00000E+05 km
Result window:
Start time, distance = 2007 FEB 04 07:01:30.094 399999.999999998
Stop time, distance = 2007 FEB 04 07:01:30.094 399999.999999998
Start time, distance = 2007 FEB 10 09:29:56.659 399999.999999989
Stop time, distance = 2007 FEB 10 09:29:56.659 399999.999999989
Start time, distance = 2007 MAR 03 00:19:19.998 399999.999999994
Stop time, distance = 2007 MAR 03 00:19:19.998 399999.999999994
Start time, distance = 2007 MAR 10 14:03:33.312 400000.000000000
Stop time, distance = 2007 MAR 10 14:03:33.312 400000.000000000
Condition: distance < 4.00000E+05 km
Result window:
Start time, distance = 2007 JAN 15 00:00:00.000 393018.609906208
Stop time, distance = 2007 FEB 04 07:01:30.094 399999.999999990
Start time, distance = 2007 FEB 10 09:29:56.659 399999.999999998
Stop time, distance = 2007 MAR 03 00:19:19.998 400000.000000006
Start time, distance = 2007 MAR 10 14:03:33.312 400000.000000010
Stop time, distance = 2007 MAR 15 00:00:00.000 376255.453934464
Condition: distance > 4.00000E+05 km
Result window:
Start time, distance = 2007 FEB 04 07:01:30.094 399999.999999990
Stop time, distance = 2007 FEB 10 09:29:56.659 399999.999999998
Start time, distance = 2007 MAR 03 00:19:19.998 400000.000000006
Stop time, distance = 2007 MAR 10 14:03:33.312 400000.000000010
Condition: distance is a local minimum
Result window:
Start time, distance = 2007 JAN 22 12:30:49.458 366925.804109350
Stop time, distance = 2007 JAN 22 12:30:49.458 366925.804109350
Start time, distance = 2007 FEB 19 09:36:29.968 361435.646812061
Stop time, distance = 2007 FEB 19 09:36:29.968 361435.646812061
Condition: distance is the absolute minimum
Result window:
Start time, distance = 2007 FEB 19 09:36:29.968 361435.646812061
Stop time, distance = 2007 FEB 19 09:36:29.968 361435.646812061
Condition: distance < the absolute minimum + 1.00000E+02 km
Result window:
Start time, distance = 2007 FEB 19 01:09:52.706 361535.646812062
Stop time, distance = 2007 FEB 19 18:07:45.136 361535.646812061
Condition: distance is a local maximum
Result window:
Start time, distance = 2007 FEB 07 12:38:29.870 404992.424288620
Stop time, distance = 2007 FEB 07 12:38:29.870 404992.424288620
Start time, distance = 2007 MAR 07 03:37:02.122 405853.452130754
Stop time, distance = 2007 MAR 07 03:37:02.122 405853.452130754
Condition: distance is the absolute maximum
Result window:
Start time, distance = 2007 MAR 07 03:37:02.122 405853.452130754
Stop time, distance = 2007 MAR 07 03:37:02.122 405853.452130754
Condition: distance > the absolute maximum - 1.00000E+02 km
Result window:
Start time, distance = 2007 MAR 06 15:56:00.957 405753.452130753
Stop time, distance = 2007 MAR 07 15:00:38.674 405753.452130753
1) The kernel files to be used by this routine must be loaded
(normally via the CSPICE routine furnsh_c) before this routine
is called.
2) This routine has the side effect of re-initializing the
distance quantity utility package.
None.
N.J. Bachman (JPL)
E.D. Wright (JPL)
-CSPICE Version 1.0.1, 28-FEB-2013 (NJB) (EDW)
Header was updated to discuss use of gfstol_c. A
header typo was corrected.
-CSPICE Version 1.0.0, 15-APR-2009 (NJB) (EDW)
GF distance search
Link to routine gfdist_c source file gfdist_c.c
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