/rust/registry/src/index.crates.io-1949cf8c6b5b557f/sofars-0.6.1/src/erst/gst06a.rs

Source
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)
}

Coverage Report

Created: 2026-07-30 06:46

Line	Count	Source
1		use super::gst06;
2		use crate::pnp::pnm06a;
3
4		/// Greenwich apparent sidereal time, IAU 2006/2000A
5		///
6		/// Greenwich apparent sidereal time (consistent with IAU 2000 and 2006
7		/// resolutions).
8		///
9		/// This function is part of the International Astronomical Union's
10		/// SOFA (Standards of Fundamental Astronomy) software collection.
11		///
12		/// Status: canonical model.
13		///
14		/// Given:
15		/// ```
16		/// uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
17		/// tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
18		/// ```
19		/// Returned (function value):
20		/// ```
21		/// double Greenwich apparent sidereal time (radians)
22		/// ```
23		/// Notes:
24		///
25		/// 1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
26		/// Julian Dates, apportioned in any convenient way between the
27		/// argument pairs. For example, JD(UT1)=2450123.7 could be
28		/// expressed in any of these ways, among others:
29		/// ```
30		/// uta utb
31		///
32		/// 2450123.7 0.0 (JD method)
33		/// 2451545.0 -1421.3 (J2000 method)
34		/// 2400000.5 50123.2 (MJD method)
35		/// 2450123.5 0.2 (date & time method)
36		/// ```
37		/// The JD method is the most natural and convenient to use in
38		/// cases where the loss of several decimal digits of resolution
39		/// is acceptable (in the case of UT; the TT is not at all critical
40		/// in this respect). The J2000 and MJD methods are good compromises
41		/// between resolution and convenience. For UT, the date & time
42		/// method is best matched to the algorithm that is used by the Earth
43		/// rotation angle function, called internally: maximum precision is
44		/// delivered when the uta argument is for 0hrs UT1 on the day in
45		/// question and the utb argument lies in the range 0 to 1, or vice
46		/// versa.
47		///
48		/// 2) Both UT1 and TT are required, UT1 to predict the Earth rotation
49		/// and TT to predict the effects of precession-nutation. If UT1 is
50		/// used for both purposes, errors of order 100 microarcseconds
51		/// result.
52		///
53		/// 3) This GAST is compatible with the IAU 2000/2006 resolutions and
54		/// must be used only in conjunction with IAU 2006 precession and
55		/// IAU 2000A nutation.
56		///
57		/// 4) The result is returned in the range 0 to 2pi.
58		///
59		/// Called:
60		/// ```
61		/// iauPnm06a classical NPB matrix, IAU 2006/2000A
62		/// iauGst06 Greenwich apparent ST, IAU 2006, given NPB matrix
63		/// ```
64		/// Reference:
65		///
66		/// Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
67		///
68	0	pub fn gst06a(uta: f64, utb: f64, tta: f64, ttb: f64) -> f64 {
69		// Classical nutation x precession x bias matrix, IAU 2000A.
70	0	let rnpb = pnm06a(tta, ttb);
71
72		// Greenwich apparent sidereal time.
73	0	gst06(uta, utb, tta, ttb, &rnpb)
74	0	}