Procedure

     SPKE09 ( S/P Kernel, evaluate, type 9 )

     SUBROUTINE SPKE09 ( ET, RECORD, STATE )

Abstract

     Evaluate a single SPK data record from a segment of type 9
     (discrete states, evaluated by Lagrange interpolation).

Required_Reading

     SPK

Keywords

     EPHEMERIS

Declarations

     IMPLICIT NONE

     INCLUDE 'spkrec.inc'

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

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     ET         I   Target epoch.
     RECORD    I-O  Data record.
     STATE      O   State (position and velocity).

Detailed_Input

     ET       is a target epoch, at which a state vector is to
              be computed.

     RECORD   is a data record which, when evaluated at epoch ET,
              will give the state (position and velocity) of some
              body, relative to some center, in some inertial
              reference frame. Normally, the caller of this routine
              will obtain RECORD by calling SPKR09.

              The structure of the record is as follows:

                 +----------------------+
                 | number of states (n) |
                 +----------------------+
                 | state 1 (6 elts.)    |
                 +----------------------+
                 | state 2 (6 elts.)    |
                 +----------------------+
                             .
                             .
                             .
                 +----------------------+
                 | state n (6 elts.)    |
                 +----------------------+
                 | epochs 1--n          |
                 +----------------------+

Detailed_Output

     RECORD   is the input record, modified by use as a work area.
              On output, RECORD no longer contains useful
              information.

     STATE    is the state. In order, the elements are

                 X, Y, Z, X', Y', and Z'

              Units are km and km/sec.

Parameters

     None.

Exceptions

     1)  The caller of this routine must ensure that the input record
         is appropriate for the supplied ET value. Otherwise,
         arithmetic overflow may result.

Files

     None.

Particulars

     The exact format and structure of type 9 (unequally spaced
     discrete states, evaluated by Lagrange interpolation) segments are
     described in the SPK Required Reading file.

Examples

     The SPKEnn routines are almost always used in conjunction with
     the corresponding SPKRnn routines, which read the records from
     SPK files.

     The data returned by the SPKRnn 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 SPKRnn
     routines might be used to examine raw segment data before
     evaluating it with the SPKEnn routines.


     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. 9 ) THEN

              CALL SPKR09 ( HANDLE, DESCR, ET, RECORD )
                  .
                  .  Look at the RECORD data.
                  .
              CALL SPKE09 ( ET, RECORD, STATE )
                  .
                  .  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)
     R.E. Thurman       (JPL)

Version

    SPICELIB Version 1.2.0, 12-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.1.0, 31-AUG-2005 (NJB)

        Updated to remove non-standard use of duplicate arguments
        in XPOSEG and LGRINT calls.

    SPICELIB Version 1.0.0, 14-AUG-1993 (NJB) (RET)