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cspice_ckcov

Table of contents
Abstract
I/O
Parameters
Examples
Particulars
Exceptions
Files
Restrictions
Required_Reading
Literature_References
Author_and_Institution
Version
Index_Entries


Abstract


   CSPICE_CKCOV finds the coverage window for a specified object in a
   specified CK file.

I/O


   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).

Parameters


   None.

Examples


   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)
      ========================================


Particulars


   This routine provides an API via which applications can determine
   the coverage a specified CK file provides for a specified
   object.

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 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.

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 cspice_furnsh.

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.

Required_Reading


   CK.REQ
   DAF.REQ
   ICY.REQ
   TIME.REQ
   WINDOWS.REQ

Literature_References


   None.

Author_and_Institution


   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   E.D. Wright         (JPL)

Version


   -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)

Index_Entries


   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



Fri Dec 31 18:43:02 2021