Procedure

     SCS2E ( SCLK string to ET )

     SUBROUTINE SCS2E ( SC, SCLKCH, ET )

Abstract

     Convert a spacecraft clock string to ephemeris seconds past
     J2000 (ET).

Required_Reading

     CK
     SCLK
     SPK
     TIME

Keywords

     CONVERSION
     TIME

Declarations

     IMPLICIT NONE

     INTEGER               SC
     CHARACTER*(*)         SCLKCH
     DOUBLE PRECISION      ET

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     SC         I   NAIF integer code for a spacecraft.
     SCLKCH     I   An SCLK string.
     ET         O   Ephemeris time, seconds past J2000.

Detailed_Input

     SC       is a NAIF ID code for a spacecraft, one of whose
              clock values is represented by SCLKCH. The set of
              supported spacecraft clocks is listed in the SCLK
              Required Reading.

     SCLKCH   is a character string representation of the
              spacecraft clock value that corresponds to ET, for
              the spacecraft specified by the input argument SC.
              SCLKCH is an absolute spacecraft clock time, so
              partition information should be included in this
              string. The precise format of SCLKCH is specified
              in the SCLK Required Reading.

Detailed_Output

     ET       is the epoch, specified as ephemeris seconds past
              J2000, that corresponds to SCLKCH.

Parameters

     None.

Exceptions

     1)  If an SCLK kernel has not been loaded, does not contain all of
         the required data, or contains invalid data, an error is
         signaled by a routine in the call tree of this routine. The
         output argument ET will not be modified. This routine assumes
         that that an SCLK kernel appropriate to the spacecraft clock
         identified by the input argument SC has been loaded.

     2)  If a leapseconds kernel is required for conversion between
         SCLK and ET but is not loaded, an error is signaled by a
         routine in the call tree of this routine. The output argument
         ET will not be modified. When using SCLK kernels that map SCLK
         to a time system other than ET (also called barycentric
         dynamical time---`TDB'), it is necessary to have a leapseconds
         kernel loaded at the time this routine is called.

         The time system that an SCLK kernel maps SCLK to is indicated
         by the variable SCLK_TIME_SYSTEM_nn in the kernel, where nn
         is the negative of the NAIF integer code for the spacecraft.
         The time system used in a kernel is TDB if and only if the
         variable is assigned the value 1.

     3)  If the value of SCLKCH is invalid, an error is signaled by a
         routine in the call tree of this routine. The output argument
         ET will not be modified.

Files

     None.

Particulars

     This routine is provided as a convenience; it is simply shorthand
     for the code fragment

        CALL SCENCD ( SC, SCLKCH, SCLKDP )
        CALL SCT2E  ( SC, SCLKDP, ET     )

     See the SCLK Required Reading for a list of the entire set of
     SCLK conversion routines.

Examples

     1)  Find the state (position and velocity) of Jupiter, as seen
         from the Galileo spacecraft, at the epoch corresponding to
         the SCLK value

            2 / 3110578:89:09

         The digit `2', followed by the forward slash, indicates that
         the time value is in the second mission partition.


            During program initialization, load the leapseconds and
            SCLK kernels. We will pretend that these files are named
            "LEAPSECONDS.KER" and "GLLSCLK.KER".  To use this code
            fragment, you must substitute the actual names of these
            kernel files for the names used here.

               C
               C     Load leapseconds and SCLK kernels:
               C
                     CALL FURNSH ( 'LEAPSECONDS.KER' )
                     CALL FURNSH ( 'GLLSCLK.KER'     )

               C
               C     Load an SPK file (again, a fictitious file)
               C     containing an ephemeris for Jupiter and the
               C     GLL orbiter's trajectory.
               C
                     CALL SPKLEF ( 'GLLSPK.KER', HANDLE )

            The Galileo spacecraft ID is -77.  Convert our SCLK
            string to ephemeris seconds past J2000, which is the
            time representation expected by SPKEZ.

                     CALL SCS2E ( -77, '2 / 3110578:89:09', ET )


            Find the state of Jupiter (body 599) as seen from Galileo
            at time ET.  To use SPKEZ, you must first load an SPK
            kernel, using the routine SPKLEF.

                     CALL SPKEZ ( 599,
                    .             ET,
                    .             REFSYS,
                    .             CORR,
                    .             -77,
                    .             STATE,
                    .             LT      )



     2)  Convert a Voyager 2 SCLK value to UTC, using calendar format,
         with 3 digits of precision in the seconds component.

            Again, your initialization code must load the leapseconds
            and SCLK kernels:

               C
               C     Load leapseconds and SCLK kernels:
               C
                     CALL FURNSH ( 'LEAPSECONDS.KER' )
                     CALL FURNSH ( 'VGR2SCLK.KER'    )


            To find the UTC value corresponding to Voyager 2 SCLK
            string

                     11389.20.768

            you can use the code fragment

                     CALL SCS2E  ( -32,  '11389.29.768',  ET  )
                     CALL ET2UTC (  ET,  'C',      3,     UTC )

Restrictions

     1)  An SCLK kernel appropriate to the spacecraft clock identified
         by SC must be loaded at the time this routine is called.

     2)  If the SCLK kernel used with this routine does not map SCLK
         directly to barycentric dynamical time, a leapseconds kernel
         must be loaded at the time this routine is called.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)
     E.D. Wright        (JPL)

Version

    SPICELIB Version 1.1.0, 06-JUL-2021 (JDR)

        Added IMPLICIT NONE statement.

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

        Moved the required readings present in $Literature_References
        section to $Required_Reading and added CK to the list.

    SPICELIB Version 1.0.4, 22-AUG-2006 (EDW)

        Replaced references to LDPOOL with references
        to FURNSH.

    SPICELIB Version 1.0.3, 09-MAR-1999 (NJB)

        Explicit list of SCLK conversion routines in $Particulars
        section has been replaced by a pointer to the SCLK Required
        Reading.

    SPICELIB Version 1.0.2, 10-APR-1992 (NJB) (WLT)

        The $Brief_I/O section now lists ET correctly as an output
        from this routine. Header was updated to reflect possibility
        of needing to load a leapseconds kernel before calling this
        routine. Comment section for permuted index source lines was
        added following the header.

    SPICELIB Version 1.0.1, 12-OCT-1990 (NJB)

        $Restrictions section no longer states that you must load the
        leapseconds kernel prior to calling this routine.

        The examples have been slightly re-written. In particular,
        they no longer use calls to CLPOOL.

    SPICELIB Version 1.0.0, 03-SEP-1990 (NJB)