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TICTOC User's Guide

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   TICTOC User's Guide
      Abstract
      Summary


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TICTOC User's Guide




Last revised on 2002 DEC 13 by E. D. Wright.



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Abstract



TICTOC is a cookbook program that demonstrates how to use Toolkit routines to convert between different time representations.



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Summary



The TICTOC `cookbook' program illustrates the use use of the two SPICE time conversion routines:

STR2ET

ET2UTC

These routines convert between UTC and ET representations of time:

UTC

is a string representation of Universal Time Coordinated, which may be in calendar, day of year, or Julian date format. UTC time strings are human-readable and thus suitable as user input.
ET

which stands for Ephemeris Time, is the double precision number of ephemeris seconds past Julian year 2000. ET time is used internally in SPICELIB routines for reading ephemeris files. (The term ``Barycentric Dynamical Time'' - TBD - is widely used in place of ET.)
When you run TICTOC, it outputs several examples of UTC time strings and their corresponding ET times. However, successful execution of the program is only the first step in learning about SPICE time conversion. Read the TICTOC source code for SPICE routines time conversion usage examples. Also, refer to Time Required Reading (time.req) and the STR2ET and ET2UTC module headers for additional information.

TICTOC requires a leapseconds kernel to run; an example leapseconds kernel, 'cook_01.tls' exists in the SPICE data directory.

The following is a sample session of a TICTOC execution.

Please note: FORTRAN and C versions of the program may output numerical values in slightly different formats.

It is assumed the kernel files used by TICTOC exist in the current directory (i.e. the directory from which your execute TICTOC). This particular session was run on an Intel box using the LINUX operating system. 

 
                    Welcome to TICTOC
 
   This program demonstrates the use of the SPICELIB
   time conversion utility routines: STR2ET and ET2UTC.
 
 
   Enter the name of a leapseconds kernel file: cook_01.tls
 
   Working ... Please wait.
 
 
         Example UTC time      :  9 JAN 1986 03:12:59.22451
 
         Corresponding ET      :  -4.41103566E+08
 
         UTC calendar format   :  1986 JAN 09 03:12:59.225
         UTC day of year format:  1986-009 // 03:12:59.225
         UTC Julian date format:  JD 2446439.634
 
   Continue? (Enter Y or N): Y
 
         Example UTC time      :  1/9/86 3:12:59.22451
 
         Corresponding ET      :  -4.41103566E+08
 
         UTC calendar format   :  1986 JAN 09 03:12:59.225
         UTC day of year format:  1986-009 // 03:12:59.225
         UTC Julian date format:  JD 2446439.634
 
   Continue? (Enter Y or N): Y
 
         Example UTC time      :  86-365//12:00
 
         Corresponding ET      :  -4.10313545E+08
 
         UTC calendar format   :  1986 DEC 31 12:00:00.000
         UTC day of year format:  1986-365 // 12:00:00.000
         UTC Julian date format:  JD 2446796.000
 
   Continue? (Enter Y or N): Y
 
         Example UTC time      :  JD 2451545
 
         Corresponding ET      :  5.71839273E+01
 
         UTC calendar format   :  2000 JAN 01 12:00:00.000
         UTC day of year format:  2000-001 // 12:00:00.000
         UTC Julian date format:  JD 2451545.000
 
   Continue? (Enter Y or N): Y
 
         Example UTC time      :  77 JUL 1
 
         Corresponding ET      :  -7.10164752E+08
 
         UTC calendar format   :  1977 JUL 01 00:00:00.000
         UTC day of year format:  1977-182 // 00:00:00.000
         UTC Julian date format:  JD 2443325.500
 
   Continue? (Enter Y or N): Y
 
         Example UTC time      :  1 JUL '29
 
         Corresponding ET      :  9.30830457E+08
 
         UTC calendar format   :  2029 JUL 01 00:00:00.000
         UTC day of year format:  2029-182 // 00:00:00.000
         UTC Julian date format:  JD 2462318.500