Procedure

     SPKPV ( S/P Kernel, position and velocity )

     SUBROUTINE SPKPV ( HANDLE, DESCR, ET, REF, STATE, CENTER )

Abstract

     Return the state (position and velocity) of a target body
     relative to some center of motion in a specified frame.

Required_Reading

     SPK

Keywords

     EPHEMERIS

Declarations

     IMPLICIT NONE

     INCLUDE               'zzctr.inc'

     INTEGER               HANDLE
     DOUBLE PRECISION      DESCR    ( 5 )
     DOUBLE PRECISION      ET
     CHARACTER*(*)         REF
     DOUBLE PRECISION      STATE    ( 6 )
     INTEGER               CENTER

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   File handle.
     DESCR      I   Segment descriptor.
     ET         I   Target epoch.
     REF        I   Target reference frame.
     STATE      O   Position, velocity.
     CENTER     O   Center of state.

Detailed_Input

     HANDLE,
     DESCR    are the file handle assigned to a SPK file, and the
              descriptor for a segment within the file. Together
              they determine the ephemeris data from which the
              state of the body is to be computed.

     ET       is the epoch (ephemeris time) at which the state
              is to be computed.

     REF      is the name of the reference frame to
              which the vectors returned by the routine should
              be rotated. This may be any frame supported by
              the SPICELIB subroutine FRMCHG.

Detailed_Output

     STATE    contains the position and velocity, at epoch ET,
              for whatever body is covered by the specified segment.
              STATE has six elements: the first three contain the
              body's position; the last three contain the body's
              velocity. These vectors are rotated into the
              specified reference frame, the origin of
              which is located at the center of motion for the
              body (see CENTER, below).  Units are always km and
              km/sec.

     CENTER   is the integer ID code of the center of motion for
              the state.

Parameters

     None.

Exceptions

     1)  If the requested reference frame is not supported by the
         current version of CHGIRF, the error SPICE(SPKREFNOTSUPP)
         is signaled.

Files

     See argument HANDLE.

Particulars

     Once SPKPV was the most basic of the SPK readers, the reader upon
     which SPKSSB, SPKAPP, and SPKEZ were built. However, its function
     has now largely been replaced by SPKPVN. SPKPV should not normally
     be called except by old software written before the release of
     SPKPVN. This routine should be considered obsolete.

Examples

     In the following code fragment, an entire SPK file is searched
     for segments containing a particular epoch. For each one found,
     the body, center, segment identifier, and range at the epoch
     are printed out.

        CALL DAFOPR ( 'TEST.SPK', HANDLE )
        CALL DAFBFS (             HANDLE )

        CALL DAFFNA ( FOUND  )

        DO WHILE ( FOUND )
           CALL DAFGS ( DESCR )
           CALL DAFUS ( DESCR, 2, 6, DC, IC )

           IF ( DC(1) .LE. ET  .AND.  ET .LE. DC(2) ) THEN
              CALL SPKPV ( HANDLE, DESCR, ET, 'J2000', STATE, CENTER )
              CALL DAFGN ( IDENT )

              WRITE (*,*)
              WRITE (*,*) 'Body   = ', IC(1)
              WRITE (*,*) 'Center = ', CENTER,
              WRITE (*,*) 'ID     = ', IDENT
              WRITE (*,*) 'Range  = ', VNORM ( STATE )
           END IF

           CALL DAFFNA ( FOUND )
        END DO

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     K.R. Gehringer     (JPL)
     J.M. Lynch         (JPL)
     H.A. Neilan        (JPL)
     B.V. Semenov       (JPL)
     W.L. Taber         (JPL)
     R.E. Thurman       (JPL)
     I.M. Underwood     (JPL)

Version

    SPICELIB Version 6.1.1, 14-APR-2021 (JDR)

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

    SPICELIB Version 6.1.0, 06-DEC-2013 (BVS) (NJB)

        Updated to save the input frame name and POOL state counter
        and to do frame name-ID conversion only if the counter has
        changed. In-line comment regarding frame change was edited.

    SPICELIB Version 6.0.0, 19-SEP-1995 (WLT)

        The routine was updated to handle non-inertial frames.

    SPICELIB Version 5.0.0, 13-MAR-1995 (KRG)

        The routine was updated to handle type 14.

        A new exception, 3, was also added.

    SPICELIB Version 4.0.0, 04-NOV-1994 (WLT)

        The routine was updated to handle type 15.

    SPICELIB Version 3.0.0, 04-AUG-1993 (NJB)

        The routine was updated to handle types 08 and 09.

    SPICELIB Version 2.0.0, 01-APR-1992 (JML)

        The routine was updated to handle type 05.

    SPICELIB Version 1.0.2, 18-JUL-1991 (NJB)

        The description of the output STATE was expanded slightly.

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

        Literature references added to the header.

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