TB TT
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.15
Description Find TB-TT offset, given TT Julian Date
Arguments and Return Values Parameters: Numeric array specifying the TT Julian Dates for which to find the TB-TT offsets. Return Value: Single-precision TB-TT offsets (in seconds)
Usage Syntax: TB_TT(JD) Terrestrial Time (TT) is a time system with no leap seconds. Otherwise it is similar to UTC (the basis for civil time), in that it is taken with respect to the rotating Earth. Barycentric Time (TB, a.k.a. Barycentric Dynamical Time or TDB), on the other hand, is referenced to the solar system's barycenter (center of mass). This function finds the difference between the two for the user-specified dates/times, which is always less than 2 milliseconds. The formula used here is just a sum of two sine functions, from the GSFC (see link). For more information, see http://heasarc.gsfc.nasa.gov/docs/xte/abc/time_tutorial.html. When TB_TT() is entered without any arguments, it prints its description, as shown below.
Examples dv> TB_TT() Find TB-TT offset, given TT Julian Date Works for array inputs Returns single-precision TB-TT offset (in seconds) TB is Barycentric Time (a.k.a. Barycentric Dynamical Time, or TDB), which is with respect to the solar system barycenter. TT is Terrestrial Time (a.k.a. Terrestrial Dynamical Time, or TDT), which is with respect to the Earth. See http://heasarc.gsfc.nasa.gov/docs/xte/abc/time_tutorial.html S.Marshall 08-11-2008 0 dv> TB_TT(JD2TT(JD(2009, 10, 1, 12, 0, 0))) -0.00165475520770997 dv> TB_TT(JD2TT(JD(2010, 1, 1, 12, 0, 0))) -6.09381022513844e-05 dv> TB_TT(JD2TT(JD(2010, 4, 1, 12, 0, 0))) 0.00165677920449525 |
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Recent Library Changes Created On: 11-18-2009 |
