Procedure

     SCTIKS ( Convert spacecraft clock string to ticks. )

     SUBROUTINE SCTIKS ( SC, CLKSTR, TICKS )

Abstract

     Convert a spacecraft clock format string to number of "ticks".

Required_Reading

     SCLK

Keywords

     CONVERSION
     TIME

Declarations

     IMPLICIT NONE

     INTEGER               SC
     CHARACTER*(*)         CLKSTR
     DOUBLE PRECISION      TICKS

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     SC         I   NAIF spacecraft identification code.
     CLKSTR     I   Character representation of a spacecraft clock.
     TICKS      O   Number of ticks represented by the clock string.

Detailed_Input

     SC       is the NAIF ID number for the spacecraft whose clock
              string is being converted.

     CLKSTR   is a character string representing a spacecraft clock
              time, WITHOUT PARTITION NUMBER.

              Using Galileo as an example, the full format is

                             wwwwwwww:xx:y:z

              where z is a mod-8 counter (values 0-7) which
              increments approximately once every 8 1/3 ms., y is a
              mod-10 counter (values 0-9) which increments once
              every time z turns over, i.e., approximately once every
              66 2/3 ms., xx is a mod-91 (values 0-90) counter
              which increments once every time y turns over, i.e.,
              once every 2/3 seconds. wwwwwwww is the Real-Time Image
              Count (RIM), which increments once every time xx turns
              over, i.e., once every 60 2/3 seconds. The roll-over
              expression for the RIM is 16777215, which corresponds
              to approximately 32 years.

              wwwwwwww, xx, y, and z are referred to interchangeably
              as the fields or components of the spacecraft clock.
              SCLK components may be separated by any of the
              following characters: ' '  '.'  ':'  ','  '-'
              Any number of spaces may separate the components and
              the delimiters. The presence of the RIM component
              is required. Successive components may be omitted, and
              in such cases are assumed to represent zero values.

              Values for the individual components may exceed the
              maximum expected values. For instance, '0:0:0:9' is
              an acceptable Galileo clock string, and will convert
              to the same number of ticks as '0:0:1:1'.

              Consecutive delimiters containing no intervening digits
              are treated as if they delimit zero components.

              Trailing zeros should always be included to match the
              length of the counter.  For example, a Galileo clock
              count of '25684.90' should not be represented as
              '25684.9'.

              Some spacecraft clock components have offset, or
              starting, values different from zero. For example,
              with an offset value of 1, a mod 20 counter would
              cycle from 1 to 20 instead of from 0 to 19.

              See the SCLK required reading for a detailed
              description of the Voyager and Mars Observer clock
              formats.

Detailed_Output

     TICKS    is the number of ticks represented by the spacecraft
              clock string. A tick is defined to be the smallest
              time increment expressible by the spacecraft clock.

              An analogy may be drawn between a spacecraft clock
              and a standard wall clock, measuring hours, minutes
              and seconds. The number of ticks represented by the
              wall clock string
                                   hh:mm:ss

              would be the number of seconds represented by that
              time.

              For example:

                       00:00:10  would convert to 10
                       00:01:00  would convert to 60
                       00:10:00  would convert to 600
                       01:00:00  would convert to 3600
                       01:01:00  would convert to 3660

              See the $Examples section below for examples for
              actual spacecraft clocks.

Parameters

     None.

Exceptions

     1)  If the spacecraft clock type is not supported, the
         error SPICE(NOTSUPPORTED) is signaled.

     2)  If any of the extracted clock components cannot be parsed as
         integers, or the string has too many components, or the value
         of one of the components is less than the offset value, then,
         an error is signaled by a routine in the call tree of this
         routine.

     3)  Invalid spacecraft ID's are not diagnosed.

Files

     None.

Particulars

     Each spacecraft is assigned a clock type code in the kernel file.
     SCTIKS calls the function SCTYPE to determine this value. If the
     clock type is supported by SPICE, then the SPICELIB routine TIKSnn
     is called to handle the actual conversion from clock format to
     number of ticks. The nn in TIKSnn refers to the spacecraft clock
     type code. Different spacecraft have distinct clock formats but
     can still be of the same clock type.

     The TIKSnn routines are entry points to the routines SCLKnn, which
     also contain the ticks-to-clock format conversion routines FMTnn.
     FMTnn is called by the subroutine SCFMT, which performs the
     inverse operation to SCTIKS.

     Note the important difference between SCENCD and SCTIKS. SCENCD
     converts a clock string to the number of ticks it represents
     since the beginning of the mission, and so uses partition
     information. SCTIKS just converts to absolute ticks.

Examples

     SCTIKS is used as part of the process of encoding spacecraft clock
     by SCENCD, though SCTIKS does not process any partition informa-
     tion.

     Another use of SCTIKS, however, is to convert a clock measurement
     to ticks for use as a tolerance for the CK reader CKGP.


     C
     C      Get the pointing from a CK file of the VGR 1 narrow angle
     C      image corresponding to a particular SCLK count.
     C
     C      Load the CK file and the kernel file containing SCLK
     C      partition information for SCENCD.
     C
            CALL CKLPF  ( 'VGR1NA.CK', HANDLE )
            CALL FURNSH ( 'SCLK.KER' )

     C
     C      Get the right ID numbers.
     C
            SC    = -31
            INSTR = -31001

     C
     C      The SCLK string includes a partition number. Pictures are
     C      never shuttered at intervals smaller than 1 MOD60 count
     C      from each other. So use 1 MOD60 count as the time
     C      tolerance.
     C
            CLKSTR = '1/20556:14:768'
            TOLSTR = '      0:01:000'

     C
     C      Encode the clock string and the tolerance.
     C
            CALL SCENCD ( SC, CLKSTR, SCLK )
            CALL SCTIKS ( SC, TOLSTR, TOL  )

     C
     C      Get the pointing from the C-kernel.
     C
            CALL CKGP ( INSTR, SCLK, TOL, REF, CMAT, CLKOUT, FOUND )



      Below are some examples illustrating various clock string inputs
      and the resulting outputs for the Galileo spacecraft. See the
      SCLK required reading for a detailed description of the Galileo
      clock format.

         CLKSTR                TICKS
         ----------------      --------------------
         '0:0:0:1'             1
         '0:0:1'               8
         '0:1'                 80
         '1'                   7280
         '1 0 0 0'             7280
         '1,0,0,0'             7280
         '1:90'                14480
         '1:9'                 8000
         '1:09'                8000
         '0-0-10'              80   |--  Third component is supposed
         '0-1-0'               80   |    to be a mod-10 count.
         '0/1/0'               Error: '/' is not an accepted delimiter.
         '1: 00 : 0 : 1'       7281
         '1:::1'               7281
         '1.1.1.1.1'           Error: Too many components
         '1.1.1.1.'            Error: The last delimiter signals that
                                      a fifth component will follow.


         The following examples are for the Voyager 2 spacecraft. Note
         that the last component of the Voyager clock has an offset
         value of 1.

         CLKSTR                TICKS
         ----------------      --------------------
          '0.0.001'              0
          '0:0:002'              1
          '0:01'                 800
          '1'                    48000
          '1.0'                  48000
          '1.0.0'                Error: The 3rd component is never 0.
          '0.0:100'              99
          '0-60-1'               48000
          '1-1-1'                48800
          '1-1-2'                48801

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     J.M. Lynch         (JPL)
     W.L. Taber         (JPL)
     R.E. Thurman       (JPL)
     E.D. Wright        (JPL)

Version

    SPICELIB Version 1.1.0, 01-NOV-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.2, 22-AUG-2006 (EDW)

        Replaced references to LDPOOL with references
        to FURNSH.

    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.0, 06-SEP-1990 (JML) (RET)