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

use super::gst06;
use crate::pnp::pnm06a;

///  Greenwich apparent sidereal time, IAU 2006/2000A
///
///  Greenwich apparent sidereal time (consistent with IAU 2000 and 2006
///  resolutions).
///
///  This function is part of the International Astronomical Union's
///  SOFA (Standards of Fundamental Astronomy) software collection.
///
///  Status:  canonical model.
///
///  Given:
///  ```
///     uta,utb    double    UT1 as a 2-part Julian Date (Notes 1,2)
///     tta,ttb    double    TT as a 2-part Julian Date (Notes 1,2)
///  ```
///  Returned (function value):
///  ```
///                double    Greenwich apparent sidereal time (radians)
///  ```
///  Notes:
///
///  1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
///     Julian Dates, apportioned in any convenient way between the
///     argument pairs.  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 (in the case of UT;  the TT is not at all critical
///     in this respect).  The J2000 and MJD methods are good compromises
///     between resolution and convenience.  For UT, the date & time
///     method is best matched to the algorithm that is used by the Earth
///     rotation angle function, called internally:  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) Both UT1 and TT are required, UT1 to predict the Earth rotation
///     and TT to predict the effects of precession-nutation.  If UT1 is
///     used for both purposes, errors of order 100 microarcseconds
///     result.
///
///  3) This GAST is compatible with the IAU 2000/2006 resolutions and
///     must be used only in conjunction with IAU 2006 precession and
///     IAU 2000A nutation.
///
///  4) The result is returned in the range 0 to 2pi.
///
///  Called:
///  ```
///     iauPnm06a    classical NPB matrix, IAU 2006/2000A
///     iauGst06     Greenwich apparent ST, IAU 2006, given NPB matrix
///  ```
///  Reference:
///
///     Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
///
pub fn gst06a(uta: f64, utb: f64, tta: f64, ttb: f64) -> f64 {
    // Classical nutation x precession x bias matrix, IAU 2000A.
    let rnpb = pnm06a(tta, ttb);

    // Greenwich apparent sidereal time.
    gst06(uta, utb, tta, ttb, &rnpb)
}