rfa 0.5.9

A port ERFA to Rust.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66

use crate::prec_nut::{obl06::*, pmat06::*};
use crate::vector_matrix::{init::ir::*, build_rotations::rx::*, matrix_ops::rxr::*};
///  ICRS equatorial to ecliptic rotation matrix, IAU 2006.
///
///  # Given:
///     date1,date2  TT as a 2-part Julian date (Note 1)
///
///  # Returned:
///     rm ICRS to ecliptic rotation 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.
///
///  1) The matrix is in the sense
///
///        E_ep = rm x P_ICRS,
///
///     where P_ICRS is a vector with respect to ICRS right ascension
///     and declination axes and E_ep is the same vector with respect to
///     the (inertial) ecliptic and equinox of date.
///
///  2) P_ICRS is a free vector, merely a direction, typically of unit
///     magnitude, and not bound to any particular spatial origin, such
///     as the Earth, Sun or SSB.  No assumptions are made about whether
///     it represents starlight and embodies astrometric effects such as
///     parallax or aberration.  The transformation is approximately that
///     between mean J2000.0 right ascension and declination and ecliptic
///     longitude and latitude, with only frame bias (always less than
///     25 mas) to disturb this classical picture.
///
///  This revision:  2021 May 11
pub fn ecm06(date1: f64, date2: f64, rm: &mut [[f64; 3];3])
{
    /* Obliquity, IAU 2006. */
       let ob = obl06(date1, date2);
    
    /* Precession-bias matrix, IAU 2006. */
    let mut bp = [[0.0; 3];3]; 
       pmat06(date1, date2, &mut bp);
    
    /* Equatorial of date to ecliptic matrix. */
    let mut e = [[0.; 3];3];       
       ir(&mut e);
       rx(ob, &mut e);
    
    /* ICRS to ecliptic coordinates rotation matrix, IAU 2006. */
       rxr(&e, &bp, rm);
}