rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use super::{c2i00a::*, pom00::*, sp00::*, c2tcio::*, };
use crate::rot_time::era00::*;
///  Form the celestial to terrestrial matrix given the date, the UT1 and
///  the polar motion, using the IAU 2000A precession-nutation model.
///
///  Given:
///   * tta,ttb  TT as a 2-part Julian Date (Note 1)
///   * uta,utb  UT1 as a 2-part Julian Date (Note 1)
///   * xp,yp    CIP coordinates (radians, Note 2)
///
///  Returned:
///   * rc2t     celestial-to-terrestrial matrix (Note 3)
///
/// # Notes:
///
///  1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
///     apportioned in any convenient way between the arguments uta and
///     utb.  For example, JD(UT1)=2450123.7 could be expressed in any of
///     these ways, among others:
///
///     |    uta      |      utb     |                      |
///     |-------------|--------------|----------------------|
///     |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 and MJD methods are good compromises
///     between resolution and convenience.  In the case of uta,utb, the
///     date & time method is best matched to the Earth rotation angle
///     algorithm used:  maximum precision is delivered when the uta
///     argument is for 0hrs UT1 on the day in question and the utb
///     argument lies in the range 0 to 1, or vice versa.
///
///  2) The arguments xp and yp are the coordinates (in radians) of the
///     Celestial Intermediate Pole with respect to the International
///     Terrestrial Reference System (see IERS Conventions 2003),
///     measured along the meridians 0 and 90 deg west respectively.
///
///  3) The matrix rc2t transforms from celestial to terrestrial
///     coordinates:
///
///        [TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
///
///              = rc2t * [CRS]
///
///     where [CRS] is a vector in the Geocentric Celestial Reference
///     System and [TRS] is a vector in the International Terrestrial
///     Reference System (see IERS Conventions 2003), RC2I is the
///     celestial-to-intermediate matrix, ERA is the Earth rotation
///     angle and RPOM is the polar motion matrix.
///
///  4) A faster, but slightly less accurate, result (about 1 mas) can
///     be obtained by using instead the eraC2t00b function.
///
/// # Called:
///    * c2i00a    celestial-to-intermediate matrix, IAU 2000A
///    * era00     Earth rotation angle, IAU 2000
///    * sp00      the TIO locator s', IERS 2000
///    * pom00     polar motion matrix
///    * c2tcio    form CIO-based celestial-to-terrestrial matrix
///
/// # Reference:
///   * McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
///     IERS Technical Note No. 32, BKG (2004)
///
///  This revision:  2021 May 11
pub fn c2t00a(tta: f64, ttb: f64, uta: f64, utb: f64,
    xp: f64, yp: f64,  rc2t: &mut [[f64;3];3])
    {
        let mut rc2i = [[0.0; 3]; 3]; let mut rpom = [[0.0; 3]; 3];
     
     
     /* Form the celestial-to-intermediate matrix for this TT (IAU 2000A). */
        c2i00a(tta, ttb, &mut rc2i );
     
     /* Predict the Earth rotation angle for this UT1. */
        let era = era00(uta, utb);
     
     /* Estimate s'. */
        let sp = sp00(tta, ttb);
     
     /* Form the polar motion matrix. */
        pom00(xp, yp, sp, &mut rpom);
     
     /* Combine to form the celestial-to-terrestrial matrix. */
        c2tcio(&rc2i, era, &rpom, rc2t);
     
     /* Finished. */
     
     }