bp00¶
- erfa.bp00(date1, date2)[source]¶
Frame bias and precession, IAU 2000.
- Parameters:
- date1double array
- date2double array
- Returns:
- rbdouble array
- rpdouble array
- rbpdouble array
Notes
Wraps ERFA function
eraBp00
. The ERFA documentation is:- - - - - - - - e r a B p 0 0 - - - - - - - - Frame bias and precession, IAU 2000. Given: date1,date2 double TT as a 2-part Julian Date (Note 1) Returned: rb double[3][3] frame bias matrix (Note 2) rp double[3][3] precession matrix (Note 3) rbp double[3][3] bias-precession matrix (Note 4) 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 rb transforms vectors from GCRS to mean J2000.0 by applying frame bias. 3) The matrix rp transforms vectors from J2000.0 mean equator and equinox to mean equator and equinox of date by applying precession. 4) The matrix rbp transforms vectors from GCRS to mean equator and equinox of date by applying frame bias then precession. It is the product rp x rb. 5) It is permissible to re-use the same array in the returned arguments. The arrays are filled in the order given. Called: eraBi00 frame bias components, IAU 2000 eraPr00 IAU 2000 precession adjustments eraIr initialize r-matrix to identity eraRx rotate around X-axis eraRy rotate around Y-axis eraRz rotate around Z-axis eraCr copy r-matrix eraRxr product of two r-matrices Reference: "Expressions for the Celestial Intermediate Pole and Celestial Ephemeris Origin consistent with the IAU 2000A precession- nutation model", Astron.Astrophys. 400, 1145-1154 (2003) n.b. The celestial ephemeris origin (CEO) was renamed "celestial intermediate origin" (CIO) by IAU 2006 Resolution 2. This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.