sofars 0.6.0

Pure Rust implementation of the IAU SOFA library
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
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105

use crate::erst::{ee00, gmst00};
use crate::pnp::{c2teqx, pn00, pom00, sp00};

///  Form the celestial to terrestrial matrix given the date, the UT1,
///  the nutation and the polar motion.  IAU 2000.
///
///  Given:
///     tta,ttb    f64        TT as a 2-part Julian Date (Note 1)
///     uta,utb    f64        UT1 as a 2-part Julian Date (Note 1)
///     dpsi,deps  f64        nutation (Note 2)
///     xp,yp      f64        coordinates of the pole (radians, Note 3)
///
///  Returned:
///     rc2t       [[f64; 3]; 3]  celestial-to-terrestrial matrix (Note 4)
///
///  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 caller is responsible for providing the nutation components;
///     they are in longitude and obliquity, in radians and are with
///     respect to the equinox and ecliptic of date.  For high-accuracy
///     applications, free core nutation should be included as well as
///     any other relevant corrections to the position of the CIP.
///
///  3) 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.
///
///  4) The matrix rc2t transforms from celestial to terrestrial
///     coordinates:
///
///        [TRS] = RPOM * R_3(GST) * RBPN * [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), RBPN is the
///     bias-precession-nutation matrix, GST is the Greenwich (apparent)
///     Sidereal Time and RPOM is the polar motion matrix.
///
///  5) Although its name does not include "00", This function is in fact
///     specific to the IAU 2000 models.
///
///  Called:
///     iauPn00      bias/precession/nutation results, IAU 2000
///     iauGmst00    Greenwich mean sidereal time, IAU 2000
///     iauSp00      the TIO locator s', IERS 2000
///     iauEe00      equation of the equinoxes, IAU 2000
///     iauPom00     polar motion matrix
///     iauC2teqx    form equinox-based celestial-to-terrestrial matrix
///
///  Reference:
///
///     McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
///     IERS Technical Note No. 32, BKG (2004)
pub fn c2tpe(
    tta: f64,
    ttb: f64,
    uta: f64,
    utb: f64,
    dpsi: f64,
    deps: f64,
    xp: f64,
    yp: f64,
) -> [[f64; 3]; 3] {
    /* Form the celestial-to-true matrix for this TT. */
    let (epsa, _, _, _, _, rbpn) = pn00(tta, ttb, dpsi, deps);

    /* Predict the Greenwich Mean Sidereal Time for this UT1 and TT. */
    let gmst = gmst00(uta, utb, tta, ttb);

    /* Predict the equation of the equinoxes given TT and nutation. */
    let ee = ee00(tta, ttb, epsa, dpsi);

    /* Estimate s'. */
    let sp = sp00(tta, ttb);

    /* Form the polar motion matrix. */
    let rpom = pom00(xp, yp, sp);

    /* Combine to form the celestial-to-terrestrial matrix. */
    c2teqx(&rbpn, gmst + ee, &rpom)
}