ET2MJD
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.15
Description Convert Ephemeris Time to UTC Modified Julian Date
Arguments and Return Values Parameters: Numeric array specifying the Ephemeris Times to convert to UTC Modified Julian Dates Return Value: The corresponding set of Modified Julian Dates
Usage Syntax: ET2MJD(ET) The Modified Julian Date is a continuous count of days since midnight UTC at the beginning of November 17, 1858 (in the Gregorian calendar). Coordinated Universal Time (UTC) is the basis for the time system used in everyday life. In order to keep UTC consistent with the Earth's slightly variable rate of rotation, leap seconds are occasionally inserted into UTC. Terrestrial Time (TT) is a time system with no leap seconds. UTC and TT run at the same rate and are referenced to the rotating Earth. Ephemeris Time (ET) is the number of seconds since noon (ET) on January 1, 2000. ET is referenced to the solar system's barycenter (center of mass). It runs at the same rate as Barycentric Time (TB, a.k.a. Barycentric Dynamical Time or TDB). Returns double-precision UTC Modified Julian Dates, accurate to about one millisecond (1e-8 of a day, if the input is that accurate). Otherwise, the returned values are as accurate as the input. The accuracy may be further limited by uncertainty in Delta-T; see the function DeltaT for details. For more information, see ftp://naif.jpl.nasa.gov/pub/naif/pds/data/ody-m-spice-6-v1.0/odsp_1000/data/lsk/naif0008.tls and http://heasarc.gsfc.nasa.gov/docs/xte/abc/time_tutorial.html. When ET2MJD() is entered without any arguments, it prints its description, as shown below.
Examples dv> ET2MJD() Find UTC Modified Julian Date, given ET Works for array inputs Returns double-precision UTC Modified Julian Date Accurate to about 1 millisecond (if the input is that accurate) The returned values are as accurate as the input, although that accuracy may be further limited by uncertainty in Delta-T. See the function DeltaT for details. See ftp://naif.jpl.nasa.gov/pub/naif/pds/data/ody-m-spice-6-v1.0/ odsp_1000/data/lsk/naif0008.tls This appears to be the same algorithm used by showtime_themis S.Marshall 04-16-2009 0 dv> a = ET2MJD(0) 51544.4992571305 dv> MJD2date(a, 3) Saturday, January 1, 2000, 11:58:55.816 UTC (Gregorian calendar) 7x1x1 array of int, bsq format [28 bytes] 2000 1 1 11 58 55 0 |
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Recent Library Changes Created On: 11-18-2009 |
