Procedure

     SPKW18 ( Write SPK segment, type 18 )

     SUBROUTINE SPKW18 (  HANDLE,  SUBTYP,  BODY,    CENTER,
    .                     FRAME,   FIRST,   LAST,    SEGID,
    .                     DEGREE,  N,       PACKTS,  EPOCHS  )

Abstract

     Write a type 18 segment to an SPK file.

Required_Reading

     NAIF_IDS
     SPC
     SPK
     TIME

Keywords

     EPHEMERIS
     FILES

Declarations

     IMPLICIT NONE

     INCLUDE 'spk18.inc'

     INTEGER               HANDLE
     INTEGER               SUBTYP
     INTEGER               BODY
     INTEGER               CENTER
     CHARACTER*(*)         FRAME
     DOUBLE PRECISION      FIRST
     DOUBLE PRECISION      LAST
     CHARACTER*(*)         SEGID
     INTEGER               DEGREE
     INTEGER               N
     DOUBLE PRECISION      PACKTS ( * )
     DOUBLE PRECISION      EPOCHS ( * )

     INTEGER               MAXDEG
     PARAMETER           ( MAXDEG = 15 )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   Handle of an SPK file open for writing.
     SUBTYP     I   SPK type 18 subtype code.
     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 packets.
     PACKTS     I   Array of packets.
     EPOCHS     I   Array of epochs corresponding to packets.
     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.

     SUBTYP   is an integer code indicating the subtype of the
              segment to be created.

     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 nominal degree of the polynomials used to
              interpolate the states contained in the input packets.
              All components of the state vectors are interpolated by
              polynomials of the specified degree, except near the
              segment boundaries, or if the total number of states in
              the segment is too few to allow interpolation using the
              specified degree.

              If the actual interpolation degree is reduced, the
              highest degree feasible degree valid for the
              interpolation type is used.

     N        is the number of packets in the input packet array.

     PACKTS   is a time-ordered array of data packets representing
              geometric states of BODY relative to CENTER, specified
              relative to FRAME. The packet structure depends on the
              segment subtype as follows:

                 Type 0 (indicated by code S18TP0):

                    x,  y,  z,  dx/dt,  dy/dt,  dz/dt,
                    vx, vy, vz, dvx/dt, dvy/dt, dvz/dt

                 where x, y, z represent Cartesian position components
                 and  vx, vy, vz represent Cartesian velocity
                 components. Note well: vx, vy, and vz *are not
                 necessarily equal* to the time derivatives of x, y,
                 and z. This packet structure mimics that of the
                 Rosetta/MEX orbit file from which the data are taken.

                 Type 1 (indicated by code S18TP1):

                    x,  y,  z,  dx/dt,  dy/dt,  dz/dt

                 where x, y, z represent Cartesian position components
                 and  vx, vy, vz represent Cartesian velocity
                 components.

              Position units are kilometers, velocity units are
              kilometers per second, and acceleration units are
              kilometers per second per second.

     EPOCHS   is an array of epochs corresponding to the members of the
              packets 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 SPKPVN 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 the window size implied by DEGREE is odd, the error
         SPICE(INVALIDDEGREE) is signaled.

     6)  If the number of packets N is not at least 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.

     11) If the subtype code is not recognized, the error
         SPICE(INVALIDVALUE) is signaled.

Files

     A new type 18 SPK segment is written to the SPK file attached
     to HANDLE.

Particulars

     This routine writes an SPK type 18 data segment to the open SPK
     file according to the format described in the type 18 section of
     the SPK Required Reading. The SPK file must have been opened with
     write access.

Examples

     Suppose that you have states and are prepared to produce
     a segment of type 18 in an SPK file.

     The following code fragment could be used to add the new segment
     to a previously opened SPK file attached to HANDLE. The file must
     have been opened with write access.

        C
        C     Create a segment identifier.
        C
                  SEGID = 'MY_SAMPLE_SPK_TYPE_18_SEGMENT'

        C
        C     Write the segment.
        C
              CALL SPKW18 (  HANDLE,  BODY,    CENTER,  FRAME,
             .               FIRST,   LAST,    SEGID,   DEGREE,
             .               N,       STATES,  EPOCHS          )

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.1.1, 09-APR-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.1.0, 21-DEC-2012 (NJB)

        Increased the minimum packet count from 1 to 2.

    SPICELIB Version 1.0.1, 29-APR-2003 (NJB)

        Description of error condition arising from invalid window
        size was corrected.

    SPICELIB Version 1.0.0, 13-MAY-2002 (NJB)