At 05:01 AM 5/14/2004, Tony Beresford wrote: >Yossi, >Off the top of my head as the saying goes I cant provide source code, >but approximate formulae are mentioned on Page B19 of the Astronomical almanac >to convert from 1. J2000 to middle of year, > 2. middle of Year to date for mean equinox. > 3.The approximate reduction for nutation is on page B20 >TLE angular co-ordinates are I understand in the frame of True Equinox of >date. >You may be able to find source code from the USNO or the SOFIA code of the IAU >Tony Beresford According to the documentation with the Celestrak Pascal library and Trakstar, SGP4 ECI references to Mean Equinox of date. This may add in a few extra steps... For J2000 to mean equinox, you'll need polar motion (precession and nutation) and the equation of the equinoxes. I tend to use Vallado, Fundamentals of Astrodynamics, as a reference for everything. --Kati ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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