ltp¶
- erfa.ltp(epj)[source]¶
Long-term precession matrix.
- Parameters:
- epjdouble array
- Returns:
- rpdouble array
Notes
Wraps ERFA function
eraLtp
. The ERFA documentation is:- - - - - - - e r a L t p - - - - - - - Long-term precession matrix. Given: epj double Julian epoch (TT) Returned: rp double[3][3] precession matrix, J2000.0 to date Notes: 1) The matrix is in the sense P_date = rp x P_J2000, where P_J2000 is a vector with respect to the J2000.0 mean equator and equinox and P_date is the same vector with respect to the mean equator and equinox of epoch epj. 2) The Vondrak et al. (2011, 2012) 400 millennia precession model agrees with the IAU 2006 precession at J2000.0 and stays within 100 microarcseconds during the 20th and 21st centuries. It is accurate to a few arcseconds throughout the historical period, worsening to a few tenths of a degree at the end of the +/- 200,000 year time span. Called: eraLtpequ equator pole, long term eraLtpecl ecliptic pole, long term eraPxp vector product eraPn normalize vector References: Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession expressions, valid for long time intervals, Astron.Astrophys. 534, A22 Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession expressions, valid for long time intervals (Corrigendum), Astron.Astrophys. 541, C1 This revision: 2023 March 19 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.