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Index Page sctiks_c

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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

       sctiks_c ( Convert spacecraft clock string to ticks. )

       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, the error
           SPICE(NOTSUPPORTED) is signaled by a routine in the call tree
           of this routine.

       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.

       4)  If the `clkstr' input string pointer is null, the error
           SPICE(NULLPOINTER) is signaled.

       5)  If the `clkstr' input string has zero length, the error
           SPICE(EMPTYSTRING) is signaled.

#### Files

       None.

#### Particulars

       Each spacecraft is assigned a clock type code in the kernel file.
       sctiks_c 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 routines to the routines SCLKnn, which
       also contain the ticks-to-clock format conversion routines FMTnn.
       FMTnn is called by the routine scfmt_c, which performs the
       inverse operation to sctiks_c.

       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

       The numerical results shown for these examples 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) sctiks_c is used as part of the process of encoding spacecraft
          clock by scencd_c, though sctiks_c does not process any partition
          information.

          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.

          In the following example, pointing for a sequence of images from
          the CASSINI Imaging Science Subsystem (ISS) is requested from
          the C-kernel using an array of character spacecraft clock counts
          as input. The clock counts attached to the output are then
          decoded to character and compared with the input strings.

          Use the CK kernel below to load the CASSINI image navigated
          spacecraft pointing and orientation data.

             04153_04182ca_ISS.bc

          Use the SCLK kernel below to load the CASSINI spacecraft clock
          time correlation data required for the conversion between
          spacecraft clock string representation and double precision
          encoding of spacecraft clock counts.

             cas00071.tsc

          Example code begins here.

          /.
             Program sctiks_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main()
          {
             /.
             The instrument we want pointing for is the CASSINI
             spacecraft. The reference frame we want is
             J2000. The spacecraft is CASSINI.
             ./

             #define  SC         -82
             #define  INST       -82000
             #define  REF        "J2000"
             #define  CK         "04153_04182ca_ISS.bc"
             #define  SCLK       "cas00071.tsc"
             #define  NPICS      4
             #define  CLKTOL     "1.0"
             #define  MAXLEN     30

             SpiceBoolean       found;

             SpiceChar          sclkin [4][25] = { {"1/1465644279.0"},
                                                   {"1/1465644281.0"},
                                                   {"1/1465644351.0"},
                                                   {"1/1465644361.0"} };
             SpiceChar          sclkout[25];

             SpiceDouble        tol;
             SpiceDouble        timein;
             SpiceDouble        timeout;
             SpiceDouble        cmat   [3][3];

             SpiceInt           handle;
             SpiceInt           i;

             /.
             Load the appropriate files. We need

                1. CK file containing pointing data.
                2. Spacecraft clock kernel file.
             ./

             cklpf_c  ( CK,  &handle );
             furnsh_c ( SCLK         );

             /.
             Convert the tolerance string to ticks.
             ./
             sctiks_c ( SC, CLKTOL, &tol );

             for ( i = 0;  i < NPICS;  i++ )
             {
                scencd_c ( SC,   sclkin[i], &timein );

                ckgp_c   ( INST,  timein,    tol,    REF,
                           cmat,  &timeout,  &found       );

                scdecd_c ( SC, timeout, MAXLEN, sclkout );

                if ( found )
                {
                   printf ( "\n"
                            "Input  s/c clock count: %s\n"
                            "Output s/c clock count: %s\n"
                            "Output C-Matrix:          \n"
                            "   %19.16f   %19.16f   %19.16f\n"
                            "   %19.16f   %19.16f   %19.16f\n"
                            "   %19.16f   %19.16f   %19.16f\n",
                            sclkin[i],
                            sclkout,
                            cmat[0][0],  cmat[0][1],  cmat[0][2],
                            cmat[1][0],  cmat[1][1],  cmat[1][2],
                            cmat[2][0],  cmat[2][1],  cmat[2][2] );
                }
                else
                {
                   printf ( "\n"
                            "Input  s/c clock count: %s\n"
                            "No pointing found.\n",
                            sclkin[i]                     );
                }
             }

             return ( 0 );
          }

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

          Input  s/c clock count: 1/1465644279.0
          No pointing found.

          Input  s/c clock count: 1/1465644281.0
          Output s/c clock count: 1/1465644281.171
          Output C-Matrix:
             -0.3353514559487096    0.8643744402056108    0.3746948466583409
             -0.9378874268129802   -0.3438519652102230   -0.0461844199616532
              0.0889189272270388   -0.3669095980487626    0.9259971766914239

          Input  s/c clock count: 1/1465644351.0
          Output s/c clock count: 1/1465644351.071
          Output C-Matrix:
             -0.3353809293975862    0.8643636382622295    0.3746933853786226
             -0.9378742920080898   -0.3438898381078248   -0.0461691632640035
              0.0889463017035304   -0.3668995504170804    0.9259985287877129

          Input  s/c clock count: 1/1465644361.0
          No pointing found.

       2) 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

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

#### Version

       -CSPICE Version 1.1.2, 01-NOV-2021 (JDR)

           Edited the header to comply with NAIF standard.

           Created complete example from existing code fragment and added
           input kernels set using PDS archived CASSINI data.

           Added entries #4 and #5 in -Exceptions section.

       -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) (JML) (RET) (WLT)

           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

    Fri Dec 31 18:41:12 2021