num00a¶
- erfa.num00a(date1, date2)[source]¶
Form the matrix of nutation for a given date, IAU 2000A model.
- Parameters:
- date1double array
- date2double array
- Returns:
- rmatndouble array
Notes
Wraps ERFA function
eraNum00a
. The ERFA documentation is:- - - - - - - - - - e r a N u m 0 0 a - - - - - - - - - - Form the matrix of nutation for a given date, IAU 2000A model. Given: date1,date2 double TT as a 2-part Julian Date (Note 1) Returned: rmatn double[3][3] nutation matrix Notes: 1) The TT date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others: date1 date2 2450123.7 0.0 (JD method) 2451545.0 -1421.3 (J2000 method) 2400000.5 50123.2 (MJD method) 2450123.5 0.2 (date & time method) The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience. 2) The matrix operates in the sense V(true) = rmatn * V(mean), where the p-vector V(true) is with respect to the true equatorial triad of date and the p-vector V(mean) is with respect to the mean equatorial triad of date. 3) A faster, but slightly less accurate, result (about 1 mas) can be obtained by using instead the eraNum00b function. Called: eraPn00a bias/precession/nutation, IAU 2000A Reference: Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 3.222-3 (p114). This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.