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)
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.
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.
dv> JD2ET(JD(2000, 1, 1, 12, 0, 0))
dv> JD2ET(JD(2010, 1, 1, 12, 0, 0))
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Created On: 11-18-2009
Modified On: 05-07-2010