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.