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cspice_sctiks

Table of contents
Abstract
I/O
Parameters
Examples
Particulars
Exceptions
Files
Restrictions
Required_Reading
Literature_References
Author_and_Institution
Version
Index_Entries


Abstract


   CSPICE_SCTIKS converts a spacecraft clock format string to
   number of "ticks."

I/O


   Given:

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

               help, sc
                  LONG = Scalar

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

               help, clkstr
                  STRING = Scalar

               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.

   the call:

      cspice_sctiks, sc, clkstr, ticks

   returns:

      ticks    the number of ticks represented by the spacecraft clock string.

               help, ticks
                  DOUBLE = Scalar

               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.

Examples


   Any numerical results shown for these examples may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

   1) Convert a CASSINI spacecraft clock format string to its
      corresponding encoded spacecraft clock ("ticks") value.

      Note that the provided character string representing the
      spacecraft clock MUST NOT HAVE PARTITION NUMBER.

      Use the SCLK kernel below to load the CASSINI spacecraft clock
      time correlation data required for conversions between different
      spacecraft clock representations.

         cas00071.tsc


      Example code begins here.


      PRO sctiks_ex1

         ;;
         ;; Load the leapseconds kernel for time conversion.
         ;;
         cspice_furnsh, 'cas00071.tsc'

         ;;
         ;; Assign values for the spacecraft ID (CASSINI).
         ;;
         SC         = -82
         CLKSTR     = '1465644281.165'

         ;;
         ;; Convert the clock string to ticks for
         ;; spacecraft 'SC'.
         ;;
         cspice_sctiks, SC, CLKSTR, ticks
         print, ' SCLK String       Number of Ticks'
         print, '--------------  --------------------'
         print, FORMAT='(2A,F20.6)', CLKSTR, '  ', ticks

         ;;
         ;; It's always good form to unload kernels after use,
         ;; particularly in IDL due to data persistence.
         ;;
         cspice_kclear

      END


      When this program was executed on a Mac/Intel/IDL8.x/64-bit
      platform, the output was:


       SCLK String       Number of Ticks
      --------------  --------------------
      1465644281.165   375204936101.000000


   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

Particulars


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

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

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 any of the input arguments, `sc' or `clkstr', is undefined,
       an error is signaled by the IDL error handling system.

   5)  If any of the input arguments, `sc' or `clkstr', is not of the
       expected type, or it does not have the expected dimensions and
       size, an error is signaled by the Icy interface.

   6)  If the output argument `ticks' is not a named variable, an
       error is signaled by the Icy interface.

Files


   None.

Restrictions


   None.

Required_Reading


   ICY.REQ
   SCLK.REQ

Literature_References


   None.

Author_and_Institution


   J. Diaz del Rio     (ODC Space)
   E.D. Wright         (JPL)

Version


   -Icy Version 1.0.1, 01-NOV-2021 (JDR)

       Edited the header to comply with NAIF standard. Extended -I/O
       section's argument descriptions. Added example's problem statement
       and meta-kernel using CASSINI PDS archived data. Added cspice_kclear
       to code example.

       Added -Parameters, -Exceptions, -Files, -Restrictions,
       -Literature_References and -Author_and_Institution sections, and
       completed -Particulars section.

       Removed reference to the routine's corresponding CSPICE header from
       -Abstract section.

       Added arguments' type and size information in the -I/O section.

   -Icy Version 1.0.0, 16-JUN-2003 (EDW)

Index_Entries


   convert spacecraft_clock string to ticks



Fri Dec 31 18:43:07 2021