Procedure

     CKW04B ( CK type 04: Begin a segment )

     SUBROUTINE CKW04B ( HANDLE, BEGTIM, INST, REF, AVFLAG, SEGID )

Abstract

     Begin a type CK04 segment in the DAF file associated with
     HANDLE. See also CKW04A and CKW04E.

Required_Reading

     CK
     DAF

Keywords

     POINTING

Declarations

     IMPLICIT NONE

     INCLUDE               'sgparam.inc'
     INCLUDE               'ckparam.inc'

     INTEGER               HANDLE
     CHARACTER*(*)         SEGID
     INTEGER               INST
     LOGICAL               AVFLAG
     CHARACTER*(*)         REF
     DOUBLE PRECISION      BEGTIM

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   The handle of an DAF file open for writing.
     SEGID      I   The string to use for segment identifier.
     INST       I   The NAIF ID code for the SC or instrument.
     AVFLAG     I   The angular rates flag.
     REF        I   The reference frame for this segment.
     BEGTIM     I   The segment coverage start encoded SCLK time

Detailed_Input

     HANDLE   is the file handle of a CK file that has been
              opened for writing.

     SEGID    is the segment identifier. CK segment identifier
              may contain up to 40 printing ASCII characters.

     INST     is the SPICE ID for the SC structure or instrument
              whose orientation are to be recorded in a CK file.

     AVFLAG   is a logical flag that indicates whether segment will
              contain angular rate information.

     REF      is the name of a reference frame that pointing is
              given with respect to, for example 'J2000'.

     BEGTIM   is the encoded SCLK time for the start of the segment
              coverage.

Detailed_Output

     None.

     The input data is used to create the segment summary for the
     segment being started in the DAF file associated with HANDLE.

     See the $Particulars section for details about the structure of a
     type 4 CK segment.

Parameters

     This subroutine makes use of parameters defined in the files
     'sgparam.inc' and 'ckparam.inc'.

Exceptions

     1)  If a file access error occurs while this routine begins a new
         type 04 segment, the error is signaled by a routine in the
         call tree of this routine.

     2)  If numeric ID for given reference frame cannot be resolved
         from it's name, the error SPICE(INVALIDREFFRAME) is signaled.

     3)  If SEGID is more than 40 characters long, the error
         SPICE(SEGIDTOOLONG) is signaled.

     4)  If SEGID contains any nonprintable characters, the error
         SPICE(NONPRINTABLECHARS) is signaled.

Files

     See HANDLE in the $Detailed_Input section.

Particulars

     This routine begins writing a type 4 CK segment to the open DAF
     file that is associated with HANDLE. The file must have been
     opened with write access.

     This routine is one of a set of three routines for creating and
     adding data to type 4 CK segments. These routines are:

        CKW04B: Begin a type 4 CK segment. This routine must be
                called before any data may be added to a type 4
                segment.

        CKW04A: Add data to a type 4 CK segment. This routine may be
                called any number of times after a call to CKW04B to
                add type 4 records to the CK segment that was
                started.

        CKW04E: End a type 4 CK segment. This routine is called to
                make the type 4 segment a permanent addition to the
                DAF file. Once this routine is called, no further type
                4 records may be added to the segment. A new segment
                must be started.

     A type 4 CK segment consists of coefficient sets for variable
     order Chebyshev polynomials over consecutive time intervals of
     a variable length. The gaps between intervals are allowed.
     The Chebyshev polynomials represent individual quaternion
     components q0, q1, q2 and q3 and individual angular velocities
     AV1, AV2 and AV3 if they are included with the data.

     The pointing data supplied to the type 4 CK writer (CKW04A)
     is packed into an array as a sequence of records,

        ----------------------------------------------------
        | Record 1 | Record 2 | .. | Record N-1 | Record N |
        ----------------------------------------------------

     with each record in data packets has the following format.

        ----------------------------------------------------
        | The midpoint of the approximation interval       |
        ----------------------------------------------------
        | The radius of the approximation interval         |
        ----------------------------------------------------
        | Number of coefficients for q0                    |
        ----------------------------------------------------
        | Number of coefficients for q1                    |
        ----------------------------------------------------
        | Number of coefficients for q2                    |
        ----------------------------------------------------
        | Number of coefficients for q3                    |
        ----------------------------------------------------
        | Number of coefficients for AV1                   |
        ----------------------------------------------------
        | Number of coefficients for AV2                   |
        ----------------------------------------------------
        | Number of coefficients for AV3                   |
        ----------------------------------------------------
        | q0 Cheby coefficients                            |
        ----------------------------------------------------
        | q1 Cheby coefficients                            |
        ----------------------------------------------------
        | q2 Cheby coefficients                            |
        ----------------------------------------------------
        | q3 Cheby coefficients                            |
        ----------------------------------------------------
        | AV1 Cheby coefficients (optional)                |
        ----------------------------------------------------
        | AV2 Cheby coefficients (optional)                |
        ----------------------------------------------------
        | AV3 Cheby coefficients (optional)                |
        ----------------------------------------------------

Examples

     Assume that we have:

        HANDLE   is the handle of an CK file opened with write
                 access.

        SEGID    is a character string of no more than 40 characters
                 which provides a pedigree for the data in the CK
                 segment we will create.

        INST     is the SPICE ID code for the instrument whose
                 pointing data is to be placed into the file.

        AVFLAG   angular rates flag.

        REFFRM   is the name of the SPICE reference frame for the
                 pointing data.

        BEGTIM   is the starting encoded SCLK time for which the
                 segment is valid.

        ENDTIM   is the ending encoded SCLK time for which the segment
                 is valid.

        N        is the number of type 4 records that we want to
                 put into a segment in an CK file.

        NPKTS    is integer array which contains the lengths of
                 variable size data packets

        RECRDS   contains N type 4 records packaged for the CK
                 file.

        SCSTRT   contains the initial encoded SC time for each of
                 the records contained in RECRDS, where

                    SCSTRT(I) < SCSTRT(I+1), I = 1, N-1

                    SCSTRT(1) <= FIRST, SCSTRT(N) < LAST

     Then the following code fragment demonstrates how to create
     a type 4 CK segment if all of the data for the segment is
     available at one time.

     C
     C     Begin the segment.
     C
           CALL CKW04B ( HANDLE, BEGTIM, INST, REF, AVFLAG, SEGID )
     C
     C     Add the data to the segment all at once.
     C
           CALL CKW04A ( HANDLE, N, NPKTS, RECRDS, SCSTRT )
     C
     C     End the segment, making the segment a permanent
     C     addition to the CK file.
     C
           CALL CKW04E ( HANDLE, ENDTIM )

Restrictions

     1)  The file containing the segment should be opened for read
         or write access either by CKOPN or DAFOPW.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     B.V. Semenov       (JPL)
     Y.K. Zaiko         (JPL)

Version

    SPICELIB Version 1.0.2, 17-AUG-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.1, 18-APR-2014 (BVS)

        Minor header edits.

    SPICELIB Version 1.0.0, 05-MAY-1999 (YKZ) (BVS)