Index Page TICTOC User's Guide

## Table of Contents

       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_c

et2utc_c

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 CSPICE time conversion. Read the TICTOC source code for CSPICE routines time conversion usage examples. Also, refer to Time Required Reading (time.req) and the str2et_c and et2utc_c module headers for additional information.

TICTOC requires a leapseconds kernel to run; an example leapseconds kernel, 'cook_01.tls' exists in the CSPICE 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 CSPICE
       time conversion utility routines: str2et_c and et2utc_c.

       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      :  -441103565.591323

             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      :  -441103565.591323

             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      :  -410313544.816091

             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      :  57.183927

             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      :  -710164751.815897

             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      :  930830457.184117

             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