/rust/registry/src/index.crates.io-1949cf8c6b5b557f/sofars-0.6.2/src/astro/apcg13.rs

Source
use crate::eph::epv00;

use super::{IauAstrom, apcg};

///  Prepare for ICRS <−> GCRS, geocentric
///
///  For a geocentric observer, prepare star-independent astrometry
///  parameters for transformations between ICRS and GCRS coordinates.
///  The caller supplies the date, and SOFA models are used to predict
///  the Earth ephemeris.
///
///  The parameters produced by this function are required in the
///  parallax, light deflection and aberration parts of the astrometric
///  transformation chain.
///
///  This function is part of the International Astronomical Union's
///  SOFA (Standards of Fundamental Astronomy) software collection.
///
///  Status:  support function.
///
///  Given:
///  ```text
///     date1  double     TDB as a 2-part...
///     date2  double     ...Julian Date (Note 1)
///  ```
///  Returned:
///  ```text
///     astrom iauASTROM* star-independent astrometry parameters:
///      pmt    double       PM time interval (SSB, Julian years)
///      eb     double[3]    SSB to observer (vector, au)
///      eh     double[3]    Sun to observer (unit vector)
///      em     double       distance from Sun to observer (au)
///      v      double[3]    barycentric observer velocity (vector, c)
///      bm1    double       sqrt(1-|v|^2): reciprocal of Lorenz factor
///      bpn    double[3][3] bias-precession-nutation matrix
///      along  double       unchanged
///      xpl    double       unchanged
///      ypl    double       unchanged
///      sphi   double       unchanged
///      cphi   double       unchanged
///      diurab double       unchanged
///      eral   double       unchanged
///      refa   double       unchanged
///      refb   double       unchanged
///  ```
///  Notes:
///
///  1) The TDB date date1+date2 is a Julian Date, apportioned in any
///     convenient way between the two arguments.  For example,
///     JD(TDB)=2450123.7 could be expressed in any of these ways, among
///     others:
///  ```text
///            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.  For most
///     applications of this function the choice will not be at all
///     critical.
///
///     TT can be used instead of TDB without any significant impact on
///     accuracy.
///
///  2) All the vectors are with respect to BCRS axes.
///
///  3) In cases where the caller wishes to supply his own Earth
///     ephemeris, the function iauApcg can be used instead of the present
///     function.
///
///  4) This is one of several functions that inserts into the astrom
///     structure star-independent parameters needed for the chain of
///     astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
///
///     The various functions support different classes of observer and
///     portions of the transformation chain:
///  ```text
///          functions         observer        transformation
///
///       iauApcg iauApcg13    geocentric      ICRS <-> GCRS
///       iauApci iauApci13    terrestrial     ICRS <-> CIRS
///       iauApco iauApco13    terrestrial     ICRS <-> observed
///       iauApcs iauApcs13    space           ICRS <-> GCRS
///       iauAper iauAper13    terrestrial     update Earth rotation
///       iauApio iauApio13    terrestrial     CIRS <-> observed
///  ```
///     Those with names ending in "13" use contemporary SOFA models to
///     compute the various ephemerides.  The others accept ephemerides
///     supplied by the caller.
///
///     The transformation from ICRS to GCRS covers space motion,
///     parallax, light deflection, and aberration.  From GCRS to CIRS
///     comprises frame bias and precession-nutation.  From CIRS to
///     observed takes account of Earth rotation, polar motion, diurnal
///     aberration and parallax (unless subsumed into the ICRS <-> GCRS
///     transformation), and atmospheric refraction.
///
///  5) The context structure astrom produced by this function is used by
///     iauAtciq* and iauAticq*.
///
///  Called:
///  ```text
///     iauEpv00     Earth position and velocity
///     iauApcg      astrometry parameters, ICRS-GCRS, geocenter
///  ```
pub fn apcg13(date1: f64, date2: f64, astrom: &mut IauAstrom) {
    /* Earth barycentric & heliocentric position/velocity (au, au/d). */
    let (ehpv, ebpv) = epv00(date1, date2).unwrap();

    /* Compute the star-independent astrometry parameters. */
    apcg(date1, date2, &ebpv, &ehpv[0], astrom);
}

Coverage Report

Created: 2026-10-28 06:40

Line	Count	Source
1		use crate::eph::epv00;
2
3		use super::{IauAstrom, apcg};
4
5		/// Prepare for ICRS <−> GCRS, geocentric
6		///
7		/// For a geocentric observer, prepare star-independent astrometry
8		/// parameters for transformations between ICRS and GCRS coordinates.
9		/// The caller supplies the date, and SOFA models are used to predict
10		/// the Earth ephemeris.
11		///
12		/// The parameters produced by this function are required in the
13		/// parallax, light deflection and aberration parts of the astrometric
14		/// transformation chain.
15		///
16		/// This function is part of the International Astronomical Union's
17		/// SOFA (Standards of Fundamental Astronomy) software collection.
18		///
19		/// Status: support function.
20		///
21		/// Given:
22		/// ```text
23		/// date1 double TDB as a 2-part...
24		/// date2 double ...Julian Date (Note 1)
25		/// ```
26		/// Returned:
27		/// ```text
28		/// astrom iauASTROM* star-independent astrometry parameters:
29		/// pmt double PM time interval (SSB, Julian years)
30		/// eb double[3] SSB to observer (vector, au)
31		/// eh double[3] Sun to observer (unit vector)
32		/// em double distance from Sun to observer (au)
33		/// v double[3] barycentric observer velocity (vector, c)
34		/// bm1 double sqrt(1-\|v\|^2): reciprocal of Lorenz factor
35		/// bpn double[3][3] bias-precession-nutation matrix
36		/// along double unchanged
37		/// xpl double unchanged
38		/// ypl double unchanged
39		/// sphi double unchanged
40		/// cphi double unchanged
41		/// diurab double unchanged
42		/// eral double unchanged
43		/// refa double unchanged
44		/// refb double unchanged
45		/// ```
46		/// Notes:
47		///
48		/// 1) The TDB date date1+date2 is a Julian Date, apportioned in any
49		/// convenient way between the two arguments. For example,
50		/// JD(TDB)=2450123.7 could be expressed in any of these ways, among
51		/// others:
52		/// ```text
53		/// date1 date2
54		///
55		/// 2450123.7 0.0 (JD method)
56		/// 2451545.0 -1421.3 (J2000 method)
57		/// 2400000.5 50123.2 (MJD method)
58		/// 2450123.5 0.2 (date & time method)
59		/// ```
60		/// The JD method is the most natural and convenient to use in cases
61		/// where the loss of several decimal digits of resolution is
62		/// acceptable. The J2000 method is best matched to the way the
63		/// argument is handled internally and will deliver the optimum
64		/// resolution. The MJD method and the date & time methods are both
65		/// good compromises between resolution and convenience. For most
66		/// applications of this function the choice will not be at all
67		/// critical.
68		///
69		/// TT can be used instead of TDB without any significant impact on
70		/// accuracy.
71		///
72		/// 2) All the vectors are with respect to BCRS axes.
73		///
74		/// 3) In cases where the caller wishes to supply his own Earth
75		/// ephemeris, the function iauApcg can be used instead of the present
76		/// function.
77		///
78		/// 4) This is one of several functions that inserts into the astrom
79		/// structure star-independent parameters needed for the chain of
80		/// astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
81		///
82		/// The various functions support different classes of observer and
83		/// portions of the transformation chain:
84		/// ```text
85		/// functions observer transformation
86		///
87		/// iauApcg iauApcg13 geocentric ICRS <-> GCRS
88		/// iauApci iauApci13 terrestrial ICRS <-> CIRS
89		/// iauApco iauApco13 terrestrial ICRS <-> observed
90		/// iauApcs iauApcs13 space ICRS <-> GCRS
91		/// iauAper iauAper13 terrestrial update Earth rotation
92		/// iauApio iauApio13 terrestrial CIRS <-> observed
93		/// ```
94		/// Those with names ending in "13" use contemporary SOFA models to
95		/// compute the various ephemerides. The others accept ephemerides
96		/// supplied by the caller.
97		///
98		/// The transformation from ICRS to GCRS covers space motion,
99		/// parallax, light deflection, and aberration. From GCRS to CIRS
100		/// comprises frame bias and precession-nutation. From CIRS to
101		/// observed takes account of Earth rotation, polar motion, diurnal
102		/// aberration and parallax (unless subsumed into the ICRS <-> GCRS
103		/// transformation), and atmospheric refraction.
104		///
105		/// 5) The context structure astrom produced by this function is used by
106		/// iauAtciq* and iauAticq*.
107		///
108		/// Called:
109		/// ```text
110		/// iauEpv00 Earth position and velocity
111		/// iauApcg astrometry parameters, ICRS-GCRS, geocenter
112		/// ```
113	0	pub fn apcg13(date1: f64, date2: f64, astrom: &mut IauAstrom) {
114		/* Earth barycentric & heliocentric position/velocity (au, au/d). */
115	0	let (ehpv, ebpv) = epv00(date1, date2).unwrap();
116
117		/* Compute the star-independent astrometry parameters. */
118	0	apcg(date1, date2, &ebpv, &ehpv[0], astrom);
119	0	}