| ckcov_c |
|
Table of contents
Procedure
ckcov_c ( CK coverage )
void ckcov_c ( ConstSpiceChar * ckfnm,
SpiceInt idcode,
SpiceBoolean needav,
ConstSpiceChar * level,
SpiceDouble tol,
ConstSpiceChar * timsys,
SpiceCell * cover )
AbstractFind the coverage window for a specified object in a specified CK file. Required_ReadingCELLS DAF CK TIME WINDOWS KeywordsPOINTING TIME UTILITY Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- ckfnm I Name of CK file. idcode I ID code of object. needav I Flag indicating whether angular velocity is needed. level I Coverage level: "SEGMENT" OR "INTERVAL". tol I Tolerance in ticks. timsys I Time system used to represent coverage. cover I-O Window giving coverage for `idcode'. Detailed_Input
ckfnm is the name of a C-kernel.
idcode is the integer ID code of an object, normally a
spacecraft structure or instrument, for which pointing
data are expected to exist in the specified CK file.
needav is a logical variable indicating whether only segments having
angular velocity are to be considered when determining
coverage. When `needav' is SPICETRUE, segments without
angular velocity don't contribute to the coverage window;
when `needav' is SPICEFALSE, all segments for `idcode' may
contribute to the coverage window.
level is the level (granularity) at which the coverage is
examined. Allowed values and corresponding meanings are:
"SEGMENT" The output coverage window contains
intervals defined by the start and stop
times of segments for the object
designated by `idcode'.
"INTERVAL" The output coverage window contains
interpolation intervals of segments for
the object designated by `idcode'. For type
1 segments, which don't have
interpolation intervals, each epoch
associated with a pointing instance is
treated as a singleton interval; these
intervals are added to the coverage
window.
All interpolation intervals are
considered to lie within the segment
bounds for the purpose of this summary:
if an interpolation interval extends
beyond the segment coverage interval,
only its intersection with the segment
coverage interval is considered to
contribute to the total coverage.
tol is a tolerance value expressed in ticks of the spacecraft
clock associated with `idcode'. Before each interval is
inserted into the coverage window, the interval is
intersected with the segment coverage interval, then if
the intersection is non-empty, it is expanded by `tol': the
left endpoint of the intersection interval is reduced by
`tol' and the right endpoint is increased by `tol'. Adjusted
interval endpoints, when expressed as encoded SCLK, never
are less than zero ticks. Any intervals that overlap as a
result of the expansion are merged.
The coverage window returned when tol > 0 indicates the
coverage provided by the file to the CK readers ckgpav_c
and ckgp_c when that value of `tol' is passed to them as an
input.
timsys is a string indicating the time system used in the output
coverage window. `timsys' may have the values:
"SCLK" Elements of `cover' are expressed in encoded
SCLK ("ticks"), where the clock is
associated with the object designated by
`idcode'.
"TDB" Elements of `cover' are expressed as seconds
past J2000 TDB.
cover is an initialized SPICE window data structure. `cover'
optionally may contain coverage data on input; on output,
the data already present in `cover' will be combined with
coverage found for the object designated by `idcode' in the
file `ckfnm'.
If `cover' contains no data on input, its size and
cardinality still must be initialized.
`cover' must be declared as a double precision SpiceCell.
CSPICE provides the following macro, which declares and
initializes the cell
SPICEDOUBLE_CELL ( cover, COVERSZ );
where COVERSZ is the maximum capacity of `cover'.
Detailed_Output
cover is a SPICE window data structure which represents the
merged coverage for `idcode'. When the coverage level is
"INTERVAL", this is the set of time intervals for which
data for `idcode' are present in the file `ckfnm', merged
with the set of time intervals present in `cover' on input.
The merged coverage is represented as the union of one or
more disjoint time intervals. The window `cover' contains
the pairs of endpoints of these intervals.
When the coverage level is "SEGMENT", `cover' is computed
in a manner similar to that described above, but the
coverage intervals used in the computation are those of
segments rather than interpolation intervals within
segments.
When `tol' is > 0, the intervals comprising the coverage
window for `idcode' are expanded by `tol' and any intervals
overlapping as a result are merged. The resulting window
is returned in `cover'. The expanded window in no case
extends beyond the segment bounds in either direction by
more than `tol'.
The interval endpoints contained in `cover' are encoded
spacecraft clock times if `timsys' is "SCLK"; otherwise the
times are converted from encoded spacecraft clock to
seconds past J2000 TDB.
See the -Examples section below for a complete example
program showing how to retrieve the endpoints from `cover'.
ParametersNone. Exceptions
1) If the input file has transfer format, the error
SPICE(INVALIDFORMAT) is signaled by a routine in the call tree
of this routine.
2) If the input file is not a transfer file but has architecture
other than DAF, the error SPICE(INVALIDARCHTYPE) is signaled
by a routine in the call tree of this routine.
3) If the input file is a binary DAF file of type other than CK,
the error SPICE(INVALIDFILETYPE) is signaled by a routine in
the call tree of this routine.
4) If the CK file cannot be opened or read, an error is signaled
by a routine in the call tree of this routine. The output
window will not be modified.
5) If the size of the output window argument `cover' is
insufficient to contain the actual number of intervals in the
coverage window for `idcode', an error is signaled by a routine
in the call tree of this routine.
6) If `tol' is negative, the error SPICE(VALUEOUTOFRANGE) is
signaled by a routine in the call tree of this routine.
7) If `level' is not recognized, the error SPICE(INVALIDOPTION)
is signaled by a routine in the call tree of this routine.
8) If `timsys' is not recognized, the error SPICE(NOTSUPPORTED)
is signaled by a routine in the call tree of this routine.
9) If a time conversion error occurs, the error is signaled by a
routine in the call tree of this routine.
10) If the output time system is TDB, the CK subsystem must be
able to map `idcode' to the ID code of the associated spacecraft
clock. If this mapping cannot be performed, an error is
signaled by a routine in the call tree of this routine.
11) If the input CK type is not one of the supported CK types, the
error SPICE(NOTSUPPORTED) is signaled by a routine in the call
tree of this routine. This problem may indicate the version of
the SPICE Toolkit being used is outdated and a new version is
required.
12) If any of the `ckfnm', `level' or `timsys' input string
pointers is null, the error SPICE(NULLPOINTER) is signaled.
13) If any of the `ckfnm', `level' or `timsys' input strings has
zero length, the error SPICE(EMPTYSTRING) is signaled.
14) If the `cover' cell argument has a type other than
SpiceDouble, the error SPICE(TYPEMISMATCH) is signaled.
Files
This routine reads a C-kernel.
If the output time system is "TDB", then a leapseconds kernel
and an SCLK kernel for the spacecraft clock associated with
`idcode' must be loaded before this routine is called.
If the ID code of the clock associated with `idcode' is not
equal to
idcode / 1000
then the kernel variable
CK_<idcode>_SCLK
must be present in the kernel pool to identify the clock
associated with `idcode'. This variable must contain the ID code
to be used for conversion between SCLK and TDB. Normally this
variable is provided in a text kernel loaded via furnsh_c.
ParticularsThis routine provides an API via which applications can determine the coverage a specified CK file provides for a specified object. 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) Display the interval-level coverage for each object in a
specified CK file. Use tolerance of zero ticks. Do not
request angular velocity. Express the results in the TDB time
system.
Find the set of objects in the file. Loop over the contents
of the ID code set: find the coverage for each item in the
set and display the coverage.
Example code begins here.
/.
Program ckcov_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Local parameters
./
#define FILSIZ 256
#define MAXIV 100000
#define WINSIZ ( 2 * MAXIV )
#define TIMLEN 51
#define MAXOBJ 1000
/.
Local variables
./
SPICEDOUBLE_CELL ( cover, WINSIZ );
SPICEINT_CELL ( ids, MAXOBJ );
SpiceChar ckfnm [ FILSIZ ];
SpiceChar lsk [ FILSIZ ];
SpiceChar sclk [ FILSIZ ];
SpiceChar timstr [ TIMLEN ];
SpiceDouble b;
SpiceDouble e;
SpiceInt i;
SpiceInt j;
SpiceInt niv;
SpiceInt obj;
/.
Load a leapseconds kernel and SCLK kernel for output time
conversion. Note that we assume a single spacecraft clock is
associated with all of the objects in the CK.
./
prompt_c ( "Name of leapseconds kernel > ", FILSIZ, lsk );
furnsh_c ( lsk );
prompt_c ( "Name of SCLK kernel > ", FILSIZ, sclk );
furnsh_c ( sclk );
/.
Get name of CK file.
./
prompt_c ( "Name of CK file > ", FILSIZ, ckfnm );
/.
Find the set of objects in the CK file.
./
ckobj_c ( ckfnm, &ids );
/.
We want to display the coverage for each object. Loop over
the contents of the ID code set, find the coverage for
each item in the set, and display the coverage.
./
for ( i = 0; i < card_c( &ids ); i++ )
{
/.
Find the coverage window for the current object.
Empty the coverage window each time so we don't
include data for the previous object.
./
obj = SPICE_CELL_ELEM_I( &ids, i );
scard_c ( 0, &cover );
ckcov_c ( ckfnm, obj, SPICEFALSE,
"INTERVAL", 0.0, "TDB", &cover );
/.
Get the number of intervals in the coverage window.
./
niv = wncard_c( &cover );
/.
Display a simple banner.
./
printf ( "%s\n", "========================================" );
printf ( "Coverage for object %d\n", (int)obj );
/.
Convert the coverage interval start and stop times to TDB
calendar strings.
./
for ( j = 0; j < niv; j++ )
{
/.
Get the endpoints of the jth interval.
./
wnfetd_c ( &cover, j, &b, &e );
/.
Convert the endpoints to TDB calendar
format time strings and display them.
./
timout_c ( b,
"YYYY MON DD HR:MN:SC.###### (TDB) ::TDB",
TIMLEN,
timstr );
printf ( "\n"
"Interval: %d\n"
"Start: %s\n",
(int)j,
timstr );
timout_c ( e,
"YYYY MON DD HR:MN:SC.###### (TDB) ::TDB",
TIMLEN,
timstr );
printf ( "Stop: %s\n", timstr );
}
printf ( "%s\n", "========================================" );
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, using the LSK file named naif0010.tls, the SCLK file
named cas00145.tsc and the CK file named 08052_08057ra.bc, the
output was:
Name of leapseconds kernel > naif0010.tls
Name of SCLK kernel > cas00145.tsc
Name of CK file > 08052_08057ra.bc
========================================
Coverage for object -82000
Interval: 0
Start: 2008 FEB 21 00:01:07.771186 (TDB)
Stop: 2008 FEB 23 22:53:30.001738 (TDB)
Interval: 1
Start: 2008 FEB 23 22:58:13.999732 (TDB)
Stop: 2008 FEB 24 02:22:25.913175 (TDB)
Interval: 2
Start: 2008 FEB 24 02:27:49.910886 (TDB)
Stop: 2008 FEB 24 19:46:33.470587 (TDB)
Interval: 3
Start: 2008 FEB 24 19:49:33.469315 (TDB)
Stop: 2008 FEB 25 04:25:21.250677 (TDB)
Interval: 4
Start: 2008 FEB 25 04:29:33.248897 (TDB)
Stop: 2008 FEB 25 15:23:44.971594 (TDB)
Interval: 5
Start: 2008 FEB 25 15:24:12.971396 (TDB)
Stop: 2008 FEB 25 20:25:04.843864 (TDB)
Interval: 6
Start: 2008 FEB 25 20:25:48.843553 (TDB)
Stop: 2008 FEB 26 00:01:04.752306 (TDB)
========================================
2) Find the segment-level coverage for the object designated by
`idcode' provided by the set of CK files loaded via a
metakernel. (The metakernel must also specify leapseconds and
SCLK kernels.) Use tolerance of zero ticks. Do not request
angular velocity. Express the results in the TDB time system.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: ckcov_ex2.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
--------- --------
naif0010.tls Leapseconds
cas00145.tsc Cassini SCLK
08052_08057ra.bc Orientation for Cassini
\begindata
KERNELS_TO_LOAD = ( 'naif0010.tls'
'cas00145.tsc'
'08052_08057ra.bc')
\begintext
End of meta-kernel
Example code begins here.
/.
Program ckcov_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Local parameters
./
#define FILSIZ 256
#define LNSIZE 81
#define MAXCOV 100000
#define WINSIZ ( 2 * MAXCOV )
#define TIMLEN 51
/.
Local variables
./
SPICEDOUBLE_CELL ( cover, WINSIZ );
SpiceBoolean found;
SpiceChar file [ FILSIZ ];
SpiceChar idch [ LNSIZE ];
SpiceChar meta [ FILSIZ ];
SpiceChar source [ FILSIZ ];
SpiceChar timstr [ TIMLEN ];
SpiceChar type [ LNSIZE ];
SpiceDouble b;
SpiceDouble e;
SpiceInt count;
SpiceInt handle;
SpiceInt i;
SpiceInt idcode;
SpiceInt niv;
/.
Prompt for the metakernel name; load the metakernel.
The metakernel lists the CK files whose coverage
for `idcode' we'd like to determine. The metakernel
must also specify a leapseconds kernel and an SCLK
kernel for the clock associated with `idcode'.
./
prompt_c ( "Name of metakernel > ", FILSIZ, meta );
furnsh_c ( meta );
/.
Get the ID code of interest.
./
prompt_c ( "Enter ID code > ", LNSIZE, idch );
prsint_c ( idch, &idcode );
/.
Find out how many kernels are loaded. Loop over the
kernels: for each loaded CK file, add its coverage
for `idcode', if any, to the coverage window.
./
ktotal_c ( "CK", &count );
for ( i = 0; i < count; i++ )
{
kdata_c ( i, "CK", FILSIZ,
LNSIZE, FILSIZ, file,
type, source, &handle, &found );
ckcov_c ( file, idcode, SPICEFALSE,
"SEGMENT", 0.0, "TDB", &cover );
}
/.
Display results.
Get the number of intervals in the coverage window.
./
niv = wncard_c( &cover );
/.
Display a simple banner.
./
printf ( "\nCoverage for object %d\n", (int)idcode );
/.
Convert the coverage interval start and stop times to TDB
calendar strings.
./
for ( i = 0; i < niv; i++ )
{
/.
Get the endpoints of the ith interval.
./
wnfetd_c ( &cover, i, &b, &e );
/.
Convert the endpoints to TDB calendar
format time strings and display them.
./
timout_c ( b,
"YYYY MON DD HR:MN:SC.###### (TDB) ::TDB",
TIMLEN,
timstr );
printf ( "\n"
"Interval: %d\n"
"Start: %s\n",
(int)i,
timstr );
timout_c ( e,
"YYYY MON DD HR:MN:SC.###### (TDB) ::TDB",
TIMLEN,
timstr );
printf ( "Stop: %s\n", timstr );
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, using the meta-kernel file named ckcov_ex2.tm and
the NAIF ID "-82000" (Cassini spacecraft bus), the output was:
Name of metakernel > ckcov_ex2.tm
Enter ID code > -82000
Coverage for object -82000
Interval: 0
Start: 2008 FEB 21 00:01:07.771186 (TDB)
Stop: 2008 FEB 26 00:01:04.752306 (TDB)
Restrictions
1) When this routine is used to accumulate coverage for `idcode'
provided by multiple CK files, the inputs `needav', `level', `tol',
and `timsys' must have the same values for all files in order
for the result to be meaningful.
Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) Version
-CSPICE Version 1.0.4, 25-AUG-2021 (JDR)
Changed input argument name "ck" to "ckfnm" for consistency
with other routines.
Edited the header to comply with NAIF standard. Added solutions using
CASSINI data.
Extended description of argument "cover" in -Detailed_Input to include
type and preferred declaration method.
Added entry #11 and updated entry #2, #3 and #8's short error message in
-Exceptions section.
-CSPICE Version 1.0.3, 12-JUL-2016 (EDW)
Edit to example program to use "%d" with explicit casts
to int for printing SpiceInts with printf.
-CSPICE Version 1.0.2, 01-JUL-2014 (NJB)
Updated index entries.
-CSPICE Version 1.0.1, 30-NOV-2007 (NJB)
Corrected bug in first example program in header:
program now empties result window prior to collecting
data for each object. Updated examples to use wncard_c
rather than card_c. Updated second example to demonstrate
segment-level summary capability.
-CSPICE Version 1.0.0, 07-JAN-2005 (NJB)
Index_Entriesget coverage window for ck_object get coverage start and stop time for ck_object get coverage start and stop time for CK frame get coverage start and stop time for CK instrument |
Fri Dec 31 18:41:02 2021