JD2ET
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.15
Description Convert UTC Julian Date to Ephemeris Time
Arguments and Return Values Parameters: Numeric array specifying the UTC Julian Dates to convert to Ephemeris Times Return Value: The corresponding set of Ephemeris Times (in seconds)
Usage Syntax: JD2ET(JD) The Julian Date (JD) is a continuous count of days since noon UTC on January 1, 4713 BCE in the proleptic Julian 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 Ephemeris Times, accurate to about 1 millisecond (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 JD2ET() is entered without any arguments, it prints its description, as shown below.
Examples dv> JD2ET() Find ET, given UTC Julian Date Works for array inputs Returns double-precision ET, in seconds 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. TDB). 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 S.Marshall 01-23-2010 0 dv> JD2ET(JD(2000, 1, 1, 12, 0, 0)) 64.1839272847311 dv> JD2ET(JD(2010, 1, 1, 12, 0, 0)) 315619266.183939 |
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Recent Library Changes Created On: 11-18-2009 |
