Index Page sctiks_c

A B C D E F G H I J K L M N O P Q R S T U V W X

Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       void sctiks_c ( SpiceInt           sc,
                       ConstSpiceChar   * clkstr,
                       SpiceDouble      * ticks   )

#### Abstract

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

#### Required_Reading

       SCLK

#### Keywords

       CONVERSION
       TIME

#### 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 then the
           error SPICE(NOTSUPPORTED) is signalled.

       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
           the error is diagnosed by routines called by this routine.

       3)  Invalid spacecraft ID's are not diagnosed.

#### Files

       None.

#### Particulars

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

#### Examples

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

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

          /.
          Get the pointing from a CK file of the VGR 1 narrow angle
          image corresponding to a particular SCLK count.

          Load the CK file and the kernel file containing SCLK
          partition information for scencd_c.
          ./
          cklpf_c  ( "vgr1na.ck", &handle );
          furnsh_c ( "sclk.ker"           );

          /.
          Get the right ID numbers.
          ./
          sc    = -31;
          instr = -31001;

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

          /.
          Encode the clock string and the tolerance.
          ./
          scencd_c ( sc, clkstr, &sclk );
          sctiks_c ( sc, tolstr, &tol  );

          /.
          Get the pointing from the C-kernel.
          ./
          ckgp_c ( 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.M. Lynch     (JPL)
       R.E. Thurman   (JPL)

#### Version

       -CSPICE Version 1.1.1, 14-AUG-2006   (EDW)

          Replace mention of ldpool_c with furnsh_c.

       -CSPICE Version 1.1.0, 08-FEB-1998 (NJB)

           References to C2F_CreateStr_Sig were removed; code was
           cleaned up accordingly.  String checks are now done using
           the macro CHKFSTR.

       -CSPICE Version 1.0.0, 25-OCT-1997 (NJB)

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

#### Index_Entries

       convert spacecraft_clock string to ticks

#### Link to routine sctiks_c source file sctiks_c.c

    Wed Apr  5 17:54:42 2017