Table of contents
CSPICE_CKCOV finds the coverage window for a specified object in a
specified CK file.
Given:
ckfnm the scalar string name of an C-kernel.
help, ckfnm
STRING = Scalar
idcode the scalar integer CK ID code of an object, normally a
spacecraft structure or instrument, for which pointing data are
expected to exist in the specified CK file.
help, idcode
LONG = Scalar
needav a scalar boolean variable indicating whether only segments
having angular velocity are to be considered when determining
coverage.
help, needav
BOOLEAN = Scalar
When `needav' is True, segments without angular velocity don't
contribute to the coverage window; when `needav' is False, all
segments for `idcode' may contribute to the coverage window.
level the scalar string defining the level (granularity) at which the
coverage is examined.
help, level
STRING = Scalar
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 the scalar double precision tolerance value expressed in ticks
of the spacecraft clock associated with `idcode'.
help, tol
DOUBLE = Scalar
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 cspice_ckgpav
and cspice_ckgp when that value of `tol' is passed to them as
an input.
timsys the scalar string indicating the time system used in the output
coverage window.
help, timsys
STRING = Scalar
`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 an initialized SPICE window data structure.
help, cover
STRUCT = cspice_celld(2*N)
`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.
the call:
cspice_ckcov, ckfnm, idcode, needav, level, tol, timsys, cover
returns:
cover a SPICE window data structure which represents the merged
coverage for `idcode'.
help, cover
STRUCT = cspice_celld(2*N)
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'.
The user must create 'cover' using cspice_celld. (Note:
a set is a type of cell).
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
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.
PRO ckcov_ex1
;;
;; From a given CK file, retrieve the list of objects listed
;; in the file then retrieve the time coverage for each object.
;;
;; Local parameters...
;;
SPICEFALSE = 0B
MAXIV = 1000
WINSIZ = 2 * MAXIV
TIMLEN = 51
MAXOBJ = 1000
;;
;; Local variables
;;
cover = cspice_celld( WINSIZ )
ids = cspice_celli( MAXOBJ )
ckfnm = ''
lsk = ''
sclk = ''
;;
;; 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.
;;
read, lsk, PROMPT='Name of leapseconds kernel > '
cspice_furnsh, lsk
read, sclk, PROMPT='Name of SCLK kernel > '
cspice_furnsh, sclk
;;
;; Get name of CK file.
;;
read, ckfnm, PROMPT='Name of CK file > '
;;
;; Find the set of objects in the CK file.
;;
cspice_ckobj, 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, cspice_card( ids ) - 1 do begin
;;
;; Find the coverage window for the current object, 'i'.
;; Empty the coverage window each time
;; so we don't include data for the previous object.
;;
obj = ids.base[ ids.data + i ]
cspice_scard, 0L, cover
cspice_ckcov, CK, obj, SPICEFALSE, 'INTERVAL', 0.D, $
'TDB', cover
;;
;; Get the number of intervals in the coverage window.
;;
niv = cspice_wncard( cover )
;;
;; Display a simple banner.
;;
print, '========================================'
print, 'Coverage for object:', obj
;;
;; Convert the coverage interval start and stop times to TDB
;; calendar strings.
;;
for j=0, niv-1 do begin
;;
;; Get the endpoints of the jth interval.
;;
cspice_wnfetd, cover, j, b, e
;;
;; Convert the endpoints to TDB calendar
;; format time strings and display them.
;; Pass the endpoints in an array, [b,e],
;; so cspice_timout returns an array of time
;; strings.
;;
cspice_timout, [b,e], $
'YYYY MON DD HR:MN:SC.### (TDB) ::TDB', $
TIMLEN ,$
timstr
print
print, 'Interval: ', j
print, 'Start : ', timstr[0]
print, 'Stop : ', timstr[1]
endfor
print, '========================================'
endfor
;;
;; It's always good form to unload kernels after use,
;; particularly in IDL due to data persistence.
;;
cspice_kclear
END
When this program was executed on a Mac/Intel/IDL8.x/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 00:01:07.771 (TDB)
Stop : 2008 FEB 23 22:53:30.001 (TDB)
Interval: 1
Start : 2008 FEB 23 22:58:13.999 (TDB)
Stop : 2008 FEB 24 02:22:25.913 (TDB)
Interval: 2
Start : 2008 FEB 24 02:27:49.910 (TDB)
Stop : 2008 FEB 24 19:46:33.470 (TDB)
Interval: 3
Start : 2008 FEB 24 19:49:33.469 (TDB)
Stop : 2008 FEB 25 04:25:21.250 (TDB)
Interval: 4
Start : 2008 FEB 25 04:29:33.248 (TDB)
Stop : 2008 FEB 25 15:23:44.971 (TDB)
Interval: 5
Start : 2008 FEB 25 15:24:12.971 (TDB)
Stop : 2008 FEB 25 20:25:04.843 (TDB)
Interval: 6
Start : 2008 FEB 25 20:25:48.843 (TDB)
Stop : 2008 FEB 26 00:01:04.752 (TDB)
========================================
This routine provides an API via which applications can determine
the coverage a specified CK file provides for a specified
object.
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 input arguments, `ckfnm', `idcode', `needav',
`level', `tol', `timsys' or `cover', is undefined, an error is
signaled by the IDL error handling system.
13) If any of the input arguments, `ckfnm', `idcode', `needav',
`level', `tol', `timsys' or `cover', is not of the expected
type, or it does not have the expected dimensions and size, an
error is signaled by the Icy interface.
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 cspice_furnsh.
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.
CK.REQ
DAF.REQ
ICY.REQ
TIME.REQ
WINDOWS.REQ
None.
N.J. Bachman (JPL)
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.1.0, 25-AUG-2021 (JDR)
Changed input argument name "ck" to "ckfnm" for consistency
with other routines.
Edited the header to comply with NAIF standard. Modified code example to
prompt for the required kernels. Extended -Index_Entries.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections.
Removed reference to the routine's corresponding CSPICE header from
-Abstract section.
Added arguments' type and size information in the -I/O section.
-Icy Version 1.0.4, 04-APR-2012 (EDW)
Corrected typo in argument name used in the call example.
Explicitly described ID variables as "CK IDs."
-Icy Version 1.0.3, 06-FEB-2008 (EDW)
Corrected typo in abstract and call example.
-Icy Version 1.0.2, 30-NOV-2007 (NJB) (EDW)
Corrected bug in the -Examples section program:
program now empties the coverage window prior to collecting
data for the current object. Updated example to
use cspice_wncard rather than cspice_card.
-Icy Version 1.0.1, 27-FEB-2007 (EDW)
Replaced cspice_unload call in example section with
cspice_kclear.
-Icy Version 1.0.0, 30-DEC-2004 (EDW)
get 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
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