Procedure

     PCKR20 ( PCK, read record from segment, type 20 )

     SUBROUTINE PCKR20 ( HANDLE, DESCR, ET, RECORD )

Abstract

     Read a single PCK data record from a segment of type 20
     (Chebyshev, derivative coefficients only).

Required_Reading

     PCK

Keywords

     ORIENTATION
     ROTATION

Declarations

     IMPLICIT NONE

     INTEGER               HANDLE
     DOUBLE PRECISION      DESCR    ( 5 )
     DOUBLE PRECISION      ET
     DOUBLE PRECISION      RECORD   ( * )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   File handle.
     DESCR      I   Segment descriptor.
     ET         I   Evaluation epoch.
     RECORD     O   Data record.

Detailed_Input

     HANDLE,
     DESCR    are the file handle and segment descriptor for
              a PCK segment of type 20.

     ET       is an epoch for which a data record from a specific
              segment is required. ET is expressed as seconds past
              J2000 TDB.

Detailed_Output

     RECORD   is the record from the specified segment which, when
              evaluated at epoch ET, will give Euler angles and
              Euler angle rates representing the orientation and
              angular velocity of the body-fixed reference frame
              associated with the segment.

              The structure of the record is as follows:

                 +--------------------------------------+
                 | record size (excluding this element) |
                 +--------------------------------------+
                 | Coverage interval midpoint           |
                 +--------------------------------------+
                 | Coverage interval radius             |
                 +--------------------------------------+
                 | Coeffs for ANGLE_1 rate              |
                 +--------------------------------------+
                 | Coeffs for ANGLE_2 rate              |
                 +--------------------------------------+
                 | Coeffs for ANGLE_3 rate              |
                 +--------------------------------------+
                 | ANGLE_1 at interval midpoint         |
                 +--------------------------------------+
                 | ANGLE_2 at interval midpoint         |
                 +--------------------------------------+
                 | ANGLE_3 at interval midpoint         |
                 +--------------------------------------+

              In the above record

                 - Times are expressed as seconds past J2000 TDB.
                 - Angular components have units of radians.
                 - Rate coefficients have units of radians/s.

              RECORD must be declared by the caller with size large
              enough to accommodate the largest record that can be
              returned by this routine.

Parameters

     None.

Exceptions

     1)  If an issue is detected while looking up PCK data, an error is
         signaled by a routine in the call tree of this routine.

Files

     See argument HANDLE.

Particulars

     See the PCK Required Reading file for a description of the
     structure of a data type 20 (Chebyshev polynomials,
     derivative coefficients only) segment.

Examples

     The data returned by the PCKRnn routine is in its rawest form,
     taken directly from the segment. As such, it will be meaningless
     to a user unless he/she understands the structure of the data type
     completely. Given that understanding, however, the PCKRxx
     routines might be used to "dump" and check segment data for a
     particular epoch.


     C
     C     Get a segment applicable to a specified frame class ID
     C     and epoch.
     C
           CALL PCKSFS ( CLSSID, ET, HANDLE, DESCR, IDENT, FOUND )

     C
     C     Look at parts of the descriptor.
     C
           CALL DAFUS ( DESCR, 2, 6, DCD, ICD )
           REF    = ICD( 2 )
           TYPE   = ICD( 3 )

           IF ( TYPE .EQ. 20 ) THEN
              CALL PCKR20 ( HANDLE, DESCR, ET, RECORD )
                  .
                  .  Look at the RECORD data.
                  .
           END IF

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     I.M. Underwood     (JPL)

Version

    SPICELIB Version 1.0.1, 12-AUG-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.0, 17-JAN-2014 (NJB) (IMU)