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bp00

sofars::pnp

Function bp00 

Source 
pub fn bp00(
    date1: f64,
    date2: f64,
) -> ([[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3])
Expand description

Frame bias and precession matrices, IAU 2000.

Frame bias and precession, IAU 2000.

This function is part of the International Astronomical Union’s SOFA (Standards of Fundamental Astronomy) software collection.

Status: canonical model.

Given: date1,date2 double TT as a 2-part Julian Date (Note 1)

Returned (function value): (rb, rp, rbp) ([[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3])

rb frame bias matrix (Note 2) rp precession matrix (Note 3) rbp 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.

Called: iauBi00 frame bias components, IAU 2000 iauPr00 IAU 2000 precession adjustments iauIr initialize r-matrix to identity iauRx rotate around X-axis iauRy rotate around Y-axis iauRz rotate around Z-axis iauCr copy r-matrix iauRxr 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

SOFA release 2023-10-11

Copyright (C) 2023 IAU SOFA Board. See notes at end.