Index Page utc2et_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 utc2et_c ( ConstSpiceChar  * utcstr,
                       SpiceDouble     * et      )

#### Abstract

       Convert an input time from Calendar or Julian Date format, UTC,
       to ephemeris seconds past J2000.

#### Required_Reading

       TIME, KERNEL

#### Keywords

       TIME

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       utcstr     I   Input time string, UTC.
       et         O   Output epoch, ephemeris seconds past J2000.

#### Detailed_Input

       utcstr      is an input time string, containing a Calendar or
                   Julian Date, UTC. Any input string acceptable to the
                   routine tpartv_ are acceptable to utc2et_c. The length
                   of utcstr should not exceed 80 characters.

#### Detailed_Output

       et          is the equivalent of utcstr, expressed in ephemeris
                   seconds past J2000. If an error occurs, or if the
                   input string is ambiguous, et is not changed.

#### Parameters

       None.

#### Exceptions

       1) If the input time string is ambiguous, the error
          SPICE(INVALIDTIMESTRING) is signalled.

       2) This routine does not attempt to account for variations
          in the length of the second that were in effect prior
          to Jan 1, 1972.  For days prior to that date, we assume
          there are exactly 86400 ephemeris seconds.

       3) The error SPICE(EMPTYSTRING) is signalled if the input
          string does not contain at least one character, since the
          input string cannot be converted to a Fortran-style string
          in this case.

       4) The error SPICE(NULLPOINTER) is signalled if the input string
          pointer is null.

#### Files

       None.

#### Particulars

       This routine handles that task of converting strings
       representing epochs in the UTC system to ephemeris seconds
       (TDB) past the epoch of the J2000 frame.

       Although this routine is intended primarily for the
       conversion of epochs during the "space age" it may also
       be used to convert much earlier epochs.  However, before
       using this routine to convert epochs prior to 1972
       you must be sure that the assumptions made by in the
       implementation are consistent with the accuracy of
       the input calendar string.

       As noted in the "Exceptions" section above, this routine
       does not attempt to account for variations in the
       length of the second that were used prior to Jan 1, 1972.
       Instead each "UTC" day prior to Jan 1, 1972 is assumed
       to have exactly 86400 TDT seconds.

    Ancient Epochs

#### Examples

       Below is a sampling of some of the time formats that
       are acceptable as inputs to utc2et_c.  A complete discussion
       of permissible formats is given in the SPICE routine
       tpartv_ as well as the User's reference file time.req
       located in the "doc" directory of the toolkit.

       ISO (T) Formats.

       String                        Year Mon  DOY DOM  HR Min Sec
       ----------------------------  ---- ---  --- ---  -- --- ------
       1996-12-18T12:28:28           1996 Dec   na  18  12  28 28
       1986-01-18T12                 1986 Jan   na  18  12  00 00
       1986-01-18T12:19              1986 Jan   na  18  12  19 00
       1986-01-18T12:19:52.18        1986 Jan   na  18  12  19 52.18
       1995-08T18:28:12              1995  na  008  na  18  28 12
       1995-18T                      1995  na  018  na  00  00 00

       Calendar Formats.

       String                        Year   Mon DOM  HR Min  Sec
       ----------------------------  ----   --- ---  -- ---  ------
       Tue Aug  6 11:10:57  1996     1996   Aug  06  11  10  57
       1 DEC 1997 12:28:29.192       1997   Dec  01  12  28  29.192
       2/3/1996 17:18:12.002         1996   Feb  03  17  18  12.002
       Mar 2 12:18:17.287 1993       1993   Mar  02  12  18  17.287
       1992 11:18:28  3 Jul          1992   Jul  03  11  18  28
       June 12, 1989 01:21           1989   Jun  12  01  21  00
       1978/3/12 23:28:59.29         1978   Mar  12  23  28  59.29
       17JUN1982 18:28:28            1982   Jun  17  18  28  28
       13:28:28.128 1992 27 Jun      1992   Jun  27  13  28  28.128
       1972 27 jun 12:29             1972   Jun  27  12  29  00
       '93 Jan 23 12:29:47.289       1993*  Jan  23  12  29  47.289
       27 Jan 3, 19:12:28.182        2027*  Jan  03  19  12  28.182
       23 A.D. APR 4, 18:28:29.29    0023** Apr  04  18  28  29.29
       18 B.C. Jun 3, 12:29:28.291   -017** Jun  03  12  29  28.291
       29 Jun  30 12:29:29.298       2029+  Jun  30  12  29  29.298
       29 Jun '30 12:29:29.298       2030*  Jun  29  12  29  29.298

       Day of Year Formats

       String                        Year  DOY HR Min Sec
       ----------------------------  ----  --- -- --- ------
       1997-162::12:18:28.827        1997  162 12  18 28.827
       162-1996/12:28:28.287         1996  162 12  28 28.287
       1993-321/12:28:28.287         1993  231 12  28 28.287
       1992 183// 12 18 19           1992  183 12  18 19
       17:28:01.287 1992-272//       1992  272 17  28 01.287
       17:28:01.282 272-1994//       1994  272 17  28 01.282
       '92-271/ 12:28:30.291         1992* 271 12  28 30.291
       92-182/ 18:28:28.281          1992* 182 18  28 28.281
       182-92/ 12:29:29.192          0182+ 092 12  29 29.192
       182-'92/ 12:28:29.182         1992  182 12  28 29.182

       Julian Date Strings

       jd 28272.291                  Julian Date   28272.291
       2451515.2981 (JD)             Julian Date 2451515.2981
       2451515.2981 JD               Julian Date 2451515.2981

                                     Abbreviations Used in Tables

                                        na    --- Not Applicable
                                        Mon   --- Month
                                        DOY   --- Day of Year
                                        DOM   --- Day of Month
                                        Wkday --- Weekday
                                        Hr    --- Hour
                                        Min   --- Minutes
                                        Sec   --- Sec

       * The default interpretation of a year that has been abbreviated
       with a leading quote as in 'xy (such as '92) is to treat
       the year as 19xy if xy > 49 and to treat it is 20xy otherwise.
       Thus '52 is interpreted as 1952 and '47 is treated as 2047.
       However, you may change the "split point" and centuries through
       use of the SPICE routine tsetyr_.  See that routine for a discussion
       of how you may reset the split point.

       ** All epochs are regarded as belonging to the Gregorian
       calendar.  We formally extend the Gregorian calendar backward
       and forward in time for all epochs.  If you have epochs belonging
       to the Julian Calendar, consult the routines tpartv_ and JUL2GR
       for a discussion concerning conversions to the Gregorian
       calendar and et.

       +  When a day of year format or calendar format string is
       input and neither of integer components of the date
       is greater than 1000, the first integer
       is regarded as being the year.

#### Restrictions

       The conversion between et and UTC depends on the values in the
       input kernel pool. The kernel pool should be loaded prior to
       calling this routine.

       Before using this routine for epochs prior to Jan 1, 1972
       be sure to check the "Particulars" section to make sure
       that the assumptions made in this routine are consistent
       with the accuracy you require for your application.

#### Literature_References

       Jesperson and Fitz-Randolph, From Sundials to Atomic Clocks,
       Dover Publications, New York, 1977.

#### Author_and_Institution

       W.L. Taber      (JPL)
       W.M. Owen       (JPL)
       I.M. Underwood  (JPL)

#### Version

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

          Re-implemented routine without dynamically allocated, temporary
          strings. Corrected typo in chkout_c module name.

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

#### Index_Entries

       utc to ephemeris time

#### Link to routine utc2et_c source file utc2et_c.c

    Wed Apr  5 17:54:46 2017