Procedure

     SPKE02 ( SPK, evaluate record, type 2 )

     SUBROUTINE SPKE02 ( ET, RECORD, XYZDOT )

Abstract

     Evaluate a single data record from an PCK or SPK segment of type
     2 (Chebyshev Polynomials, 3 components).

Required_Reading

     SPK
     PCK

Keywords

     EPHEMERIS

Declarations

     DOUBLE PRECISION      ET
     DOUBLE PRECISION      RECORD   ( * )
     DOUBLE PRECISION      XYZDOT   ( 6 )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     ET         I   Evaluation epoch.
     RECORD     I   Data record.
     XYZDOT     O   Three function components and their derivatives.

Detailed_Input

     ET       is the epoch at which a state vector or Euler angle
              state is to be computed. The epoch is represented as
              seconds past J2000 TDB.

     RECORD   is a data record which, when evaluated at epoch ET,
              will yield three function components and their
              derivatives with respect to time. The record
              structure for SPK type 2 data is:

                 +--------------------------------------+
                 | record size (excluding this element) |
                 +--------------------------------------+
                 | Coverage interval midpoint           |
                 +--------------------------------------+
                 | Coverage interval radius             |
                 +--------------------------------------+
                 | Coeffs for X position component      |
                 +--------------------------------------+
                 | Coeffs for Y position component      |
                 +--------------------------------------+
                 | Coeffs for Z position component      |
                 +--------------------------------------+

              In the above record

                 - Times are expressed as seconds past J2000 TDB.
                 - Position components have units of km.

              See PCKE02 for a description of PCK type 2 records.

              RECORD must be declared by the caller with size large
              enough to accommodate the largest record that can be
              returned by this routine. See the INCLUDE file
              spkrec.inc for the correct record length.

Detailed_Output

     XYZDOT   is a 6-vector. In order, the components of XYZDOT are
              X, Y, Z, X', Y', and Z'. Units for state evaluations
              will be km and km/sec. Units for angles will be
              radians and radians/sec.

Parameters

     None.

Exceptions

     1)  If the input record contains an invalid coefficient count,
         the error SPICE(INVALIDCOUNT) is signaled.

     2)  If the input record contains invalid domain transformation
         parameters, an error is signaled by a routine in the
         call tree of this routine.

Files

     None.

Particulars

     The exact format and structure of type 2 (Chebyshev polynomials,
     position only) segments are described in the SPK and PCK Required
     Reading files.

     A type 2 segment contains three sets of Chebyshev coefficients,
     one set each for components X, Y, and Z. SPKE02 calls the routine
     CHBINT for each set to evaluate the polynomial AND its first
     derivative (which it computes internally) at the input epoch,
     thereby arriving at the complete state.

Examples

     The data returned by the 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.


     C
     C     Get a segment applicable to a specified body and epoch.
     C
           CALL SPKSFS ( BODY, ET, HANDLE, DESCR, IDENT, FOUND )

     C
     C     Look at parts of the descriptor.
     C
           CALL DAFUS ( DESCR, 2, 6, DCD, ICD )
           CENTER = ICD( 2 )
           REF    = ICD( 3 )
           TYPE   = ICD( 4 )

           IF ( TYPE .EQ. 2 ) THEN

              CALL SPKR02 ( HANDLE, DESCR, ET, RECORD )
                  .
                  .  Look at the RECORD data.
                  .
              CALL SPKE02 ( ET, RECORD, XYZDOT )
                  .
                  .  Check out the evaluated state.
                  .
           END IF

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     H.A. Neilan        (JPL)
     W.L. Taber         (JPL)
     R.E. Thurman       (JPL)
     K.S. Zukor         (JPL)

Version

    SPICELIB Version 2.0.1, 14-APR-2021 (JDR)

        Edited the header to comply with NAIF standard. Moved SPK
        required reading from $Literature_References to
        $Required_Reading section.

    SPICELIB Version 2.0.0, 18-JAN-2014 (NJB)

        Added error checks for invalid coefficient counts
        and invalid interval radius. Changed error handling
        style to "discovery." Enhanced header documentation.

    SPICELIB Version 1.0.4, 22-MAR-1994 (KSZ)

     Comments changed so this can be used as
     a generic Chebyshev evaluator, rather than just for
     SPK type 2 files.  (KSZ)

    SPICELIB Version 1.0.3, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.2, 23-AUG-1991 (HAN)

        SPK02 was removed from the $Required_Reading section of the
        header. The information in the SPK02 Required Reading file
        is now part of the SPK Required Reading file.

    SPICELIB Version 1.0.1, 22-MAR-1990 (HAN)

        Literature references added to the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (RET)