Procedure

     SPKW13 ( Write SPK segment, type 13 )

     SUBROUTINE SPKW13 (  HANDLE,  BODY,    CENTER,  FRAME,
    .                     FIRST,   LAST,    SEGID,   DEGREE,
    .                     N,       STATES,  EPOCHS           )

Abstract

     Write a type 13 segment to an SPK file.

Required_Reading

     NAIF_IDS
     SPC
     SPK
     TIME

Keywords

     EPHEMERIS
     FILES

Declarations

     IMPLICIT NONE

     INTEGER               HANDLE
     INTEGER               BODY
     INTEGER               CENTER
     CHARACTER*(*)         FRAME
     DOUBLE PRECISION      FIRST
     DOUBLE PRECISION      LAST
     CHARACTER*(*)         SEGID
     INTEGER               DEGREE
     INTEGER               N
     DOUBLE PRECISION      STATES ( 6, * )
     DOUBLE PRECISION      EPOCHS (    * )

     INTEGER               MAXDEG
     PARAMETER           ( MAXDEG = 27 )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   Handle of an SPK file open for writing.
     BODY       I   NAIF code for an ephemeris object.
     CENTER     I   NAIF code for center of motion of BODY.
     FRAME      I   Reference frame name.
     FIRST      I   Start time of interval covered by segment.
     LAST       I   End time of interval covered by segment.
     SEGID      I   Segment identifier.
     DEGREE     I   Degree of interpolating polynomials.
     N          I   Number of states.
     STATES     I   Array of states.
     EPOCHS     I   Array of epochs corresponding to states.
     MAXDEG     P   Maximum allowed degree of interpolating polynomial.

Detailed_Input

     HANDLE   is the file handle of an SPK file that has been
              opened for writing.

     BODY     is the NAIF integer code for an ephemeris object
              whose state relative to another body is described
              by the segment to be created.

     CENTER   is the NAIF integer code for the center of motion
              of the object identified by BODY.

     FRAME    is the NAIF name for a reference frame
              relative to which the state information for BODY
              is specified.

     FIRST,
     LAST     are, respectively, the start and stop times of
              the time interval over which the segment defines
              the state of BODY.

     SEGID    is the segment identifier. An SPK segment
              identifier may contain up to 40 characters.

     DEGREE   is the degree of the Hermite polynomials used to
              interpolate the states. All components of the
              state vectors are interpolated by polynomials of
              fixed degree.

     N        is the number of states in the input state vector
              array.

     STATES   contains a time-ordered array of geometric states
              ( x, y, z, dx/dt, dy/dt, dz/dt, in kilometers and
              kilometers per second ) of BODY relative to CENTER,
              specified relative to FRAME.

     EPOCHS   is an array of epochs corresponding to the members
              of the state array. The epochs are specified as
              seconds past J2000, TDB.

Detailed_Output

     None. See $Particulars for a description of the effect of this
     routine.

Parameters

     MAXDEG   is the maximum allowed degree of the interpolating
              polynomial. If the value of MAXDEG is increased,
              the SPICELIB routine SPKPV must be changed
              accordingly. In particular, the size of the
              record passed to SPKRnn and SPKEnn must be
              increased, and comments describing the record size
              must be changed.

Exceptions

     If any of the following exceptions occur, this routine will return
     without creating a new segment.

     1)  If FRAME is not a recognized name, the error
         SPICE(INVALIDREFFRAME) is signaled.

     2)  If the last non-blank character of SEGID occurs past index 40,
         the error SPICE(SEGIDTOOLONG) is signaled.

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

     4)  If DEGREE is not at least 1 or is greater than MAXDEG, the
         error SPICE(INVALIDDEGREE) is signaled.

     5)  If DEGREE is not odd, the error SPICE(INVALIDDEGREE) is
         signaled.

     6)  If the number of states N is not at least (DEGREE+1)/2,
         the error SPICE(TOOFEWSTATES) is signaled.

     7)  If FIRST is greater than or equal to LAST, the error
         SPICE(BADDESCRTIMES) is signaled.

     8)  If the elements of the array EPOCHS are not in strictly
         increasing order, the error SPICE(TIMESOUTOFORDER) is
         signaled.

     9)  If the first epoch, EPOCHS(1), is greater than FIRST, the
         error SPICE(BADDESCRTIMES) is signaled.

     10) If the last epoch, EPOCHS(N), is less than LAST, the error
         SPICE(BADDESCRTIMES) is signaled.

Files

     A new type 13 SPK segment is written to the SPK file attached
     to HANDLE.

Particulars

     This routine writes an SPK type 13 data segment to the open SPK
     file according to the format described in the type 13 section of
     the SPK Required Reading. The SPK file must have been opened with
     write access.

Examples

     The numerical results shown for this example may differ across
     platforms. The results depend on the SPICE kernels used as
     input, the compiler and supporting libraries, and the machine
     specific arithmetic implementation.

     1) Suppose that you have a time-ordered array of geometric states
        of a new object that follows Phobos, with a delay of 1 hour,
        in its orbit around Mars and are prepared to produce a segment
        of type 13 in an SPK file. Create a new SPK file with this
        segment. Use an existing SPK to create the input data for the
        SPK segment.

        Use the meta-kernel shown below to load the required SPICE
        kernels.


           KPL/MK

           File: spkw13_ex1.tm

           This meta-kernel is intended to support operation of SPICE
           example programs. The kernels shown here should not be
           assumed to contain adequate or correct versions of data
           required by SPICE-based user applications.

           In order for an application to use this meta-kernel, the
           kernels referenced here must be present in the user's
           current working directory.

           The names and contents of the kernels referenced
           by this meta-kernel are as follows:

              File name                        Contents
              ---------                        --------
              mar097.bsp                       Mars satellite ephemeris
              naif0012.tls                     Leapseconds

           \begindata

              KERNELS_TO_LOAD = ( 'mar097.bsp',
                                  'naif0012.tls' )

           \begintext

           End of meta-kernel


        Example code begins here.


              PROGRAM SPKW13_EX1
              IMPLICIT NONE

        C
        C     SPICELIB functions
        C
              DOUBLE PRECISION      HALFPI

        C
        C     Local parameters.
        C
              CHARACTER*(*)         SPKNAM
              PARAMETER           ( SPKNAM = 'spkw13_ex1.bsp' )

              INTEGER               DEGREE
              PARAMETER           ( DEGREE = 3   )

              INTEGER               MARS
              PARAMETER           ( MARS   = 499 )

              INTEGER               NAMLEN
              PARAMETER           ( NAMLEN = 255 )

              INTEGER               NEPOCS
              PARAMETER           ( NEPOCS = 800 )

              INTEGER               NOBJ
              PARAMETER           ( NOBJ   = 403 )

        C
        C     Local variables.
        C
              CHARACTER*(NAMLEN)    IFNAME
              CHARACTER*(NAMLEN)    SEGID

              DOUBLE PRECISION      DELTA
              DOUBLE PRECISION      ET
              DOUBLE PRECISION      EPOCHS ( NEPOCS )
              DOUBLE PRECISION      LT
              DOUBLE PRECISION      STATE  ( 6 )
              DOUBLE PRECISION      STATES ( 6, NEPOCS )
              DOUBLE PRECISION      STEP
              DOUBLE PRECISION      TIME

              INTEGER               I
              INTEGER               HANDLE

        C
        C     Load the input SPK file.
        C
              CALL FURNSH ( 'spkw13_ex1.tm' )

        C
        C     Convert the input UTC to ephemeris time
        C
              CALL STR2ET ( '2018 Apr 03 08:35', ET )

        C
        C     Create the time-ordered array of geometric states,
        C     at unequal time steps.
        C
              TIME  = ET
              STEP  = 60.D0
              DELTA = 10.D0

              DO I=1, NEPOCS

                 CALL SPKEZR ( 'PHOBOS', TIME,       'J2000', 'NONE',
             .                 'MARS',   STATES(1,I), LT             )

                 EPOCHS(I) = TIME + 3600.D0
                 TIME = TIME + STEP +
             .          SIN( HALFPI() * I / 2.D0 ) * DELTA

              END DO

        C
        C     Open a new SPK file, with 5000 characters reserved
        C     for comments.
        C
              IFNAME = 'Test SPK type 13 internal filename.'
              CALL SPKOPN ( SPKNAM, IFNAME, 5000, HANDLE )

        C
        C     Create a segment identifier.
        C
              SEGID = 'MY_SAMPLE_SPK_TYPE_13_SEGMENT'


        C
        C     Write the segment.
        C
              CALL SPKW13 ( HANDLE,    NOBJ,           MARS,  'J2000',
             .              EPOCHS(1), EPOCHS(NEPOCS), SEGID,  DEGREE,
             .              NEPOCS,    STATES,         EPOCHS        )

        C
        C     Close the new SPK file.
        C
              CALL SPKCLS ( HANDLE )

        C
        C     Compute the state of Phobos as seen from Mars,
        C     12 hours after the input UTC time.
        C
              ET = ET + 43200.0D0
              CALL SPKEZR ( 'PHOBOS', ET, 'J2000', 'NONE', 'MARS',
             .               STATE,   LT                         )

              WRITE (*,'(A)') 'Phobos as seen from Mars'
              WRITE (*,'(A,F20.6)') '   Epoch       (s):', ET
              WRITE (*,'(A,3F14.6)') '   Position   (km):',
             .                                   (STATE(I), I=1,3)
              WRITE (*,'(A,3F14.6)') '   Velocity (km/s):',
             .                                   (STATE(I), I=4,6)
              WRITE (*,*)

        C
        C     Load the newly created kernel, and compute the state
        C     of the new object as seen from Mars, 13 hours after
        C     the input UTC time.
        C
              CALL FURNSH ( SPKNAM )
              ET = ET + 3600.0D0

              CALL SPKEZR ( '403', ET, 'J2000', 'NONE', 'MARS',
             .               STATE,   LT                       )

              WRITE (*,'(A)') 'Object 403 as seen from Mars'
              WRITE (*,'(A,F20.6)') '   Epoch       (s):', ET
              WRITE (*,'(A,3F14.6)') '   Position   (km):',
             .                                   (STATE(I), I=1,3)
              WRITE (*,'(A,3F14.6)') '   Velocity (km/s):',
             .                                   (STATE(I), I=4,6)

              END


        When this program was executed on a Mac/Intel/gfortran/64-bit
        platform, the output was:


        Phobos as seen from Mars
           Epoch       (s):    576059769.185657
           Position   (km):  -7327.262770   2414.326550   5207.106376
           Velocity (km/s):     -0.942893     -1.894731     -0.396715

        Object 403 as seen from Mars
           Epoch       (s):    576063369.185657
           Position   (km):  -7327.262770   2414.326550   5207.106376
           Velocity (km/s):     -0.942893     -1.894731     -0.396715


        Note that after run completion, a new SPK file exists in
        the output directory.

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 2.0.1, 05-JUL-2021 (JDR)

        Edited the header to comply with NAIF standard. Removed
        unnecessary $Revisions section.

    SPICELIB Version 2.0.0, 23-DEC-2013 (NJB)

        Increased MAXDEG to 27 for compatibility
        with SPK type 21. Deleted declaration of
        unused parameter TYPIDX.

    SPICELIB Version 1.0.0, 20-MAR-2000 (NJB)