Function pmat00

pub fn pmat00(date1: f64, date2: f64) -> [[f64; 3]; 3]

Expand description

Precession matrix (including frame bias) from GCRS to a specified date, IAU 2000 model.

Given: date1,date2 f64 TT as a 2-part Julian Date (Note 1)

Returned (function value): [[f64; 3]; 3] bias-precession matrix (Note 2)

Notes:

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.
The matrix operates in the sense V(date) = rbp * V(GCRS), where the p-vector V(GCRS) is with respect to the Geocentric Celestial Reference System (IAU, 2000) and the p-vector V(date) is with respect to the mean equatorial triad of the given date.

Called: iauBp00 frame bias and precession matrices, IAU 2000

Reference:

IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc. 24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6. (2000)

pmat00