#include "sofa.h"
#include "sofam.h"
void iauApcs(double date1, double date2, double pv[2][3],
double ebpv[2][3], double ehp[3],
iauASTROM *astrom)
/*
** - - - - - - - -
** i a u A p c s
** - - - - - - - -
**
** For an observer whose geocentric position and velocity are known,
** prepare star-independent astrometry parameters for transformations
** between ICRS and GCRS. The Earth ephemeris is supplied by the
** caller.
**
** The parameters produced by this function are required in the space
** motion, 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:
** date1 double TDB as a 2-part...
** date2 double ...Julian Date (Note 1)
** pv double[2][3] observer's geocentric pos/vel (m, m/s)
** ebpv double[2][3] Earth barycentric PV (au, au/day)
** ehp double[3] Earth heliocentric P (au)
**
** Returned:
** 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:
**
** 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) Providing separate arguments for (i) the observer's geocentric
** position and velocity and (ii) the Earth ephemeris is done for
** convenience in the geocentric, terrestrial and Earth orbit cases.
** For deep space applications it maybe more convenient to specify
** zero geocentric position and velocity and to supply the
** observer's position and velocity information directly instead of
** with respect to the Earth. However, note the different units:
** m and m/s for the geocentric vectors, au and au/day for the
** heliocentric and barycentric vectors.
**
** 4) In cases where the caller does not wish to provide the Earth
** ephemeris, the function iauApcs13 can be used instead of the
** present function. This computes the Earth ephemeris using the
** SOFA function iauEpv00.
**
** 5) 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:
**
** 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.
**
** 6) The context structure astrom produced by this function is used by
** iauAtciq* and iauAticq*.
**
** Called:
** iauCp copy p-vector
** iauPm modulus of p-vector
** iauPn decompose p-vector into modulus and direction
** iauIr initialize r-matrix to identity
**
** This revision: 2021 February 24
**
** SOFA release 2021-05-12
**
** Copyright (C) 2021 IAU SOFA Board. See notes at end.
*/
{
/* au/d to m/s */
const double AUDMS = DAU/DAYSEC;
/* Light time for 1 au (day) */
const double CR = AULT/DAYSEC;
int i;
double dp, dv, pb[3], vb[3], ph[3], v2, w;
/* Time since reference epoch, years (for proper motion calculation). */
astrom->pmt = ( (date1 - DJ00) + date2 ) / DJY;
/* Adjust Earth ephemeris to observer. */
for (i = 0; i < 3; i++) {
dp = pv[0][i] / DAU;
dv = pv[1][i] / AUDMS;
pb[i] = ebpv[0][i] + dp;
vb[i] = ebpv[1][i] + dv;
ph[i] = ehp[i] + dp;
}
/* Barycentric position of observer (au). */
iauCp(pb, astrom->eb);
/* Heliocentric direction and distance (unit vector and au). */
iauPn(ph, &astrom->em, astrom->eh);
/* Barycentric vel. in units of c, and reciprocal of Lorenz factor. */
v2 = 0.0;
for (i = 0; i < 3; i++) {
w = vb[i] * CR;
astrom->v[i] = w;
v2 += w*w;
}
astrom->bm1 = sqrt(1.0 - v2);
/* Reset the NPB matrix. */
iauIr(astrom->bpn);
/* Finished. */
/*----------------------------------------------------------------------
**
** Copyright (C) 2021
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
** include the prefix "iau" or "sofa" or trivial modifications
** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
** not be misrepresented; you must not claim that you wrote the
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**
** e) These requirements must be reproduced intact in any source
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**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
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**
** 5. The SOFA software is provided "as is" and SOFA makes no warranty
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**
** 6. The provision of any version of the SOFA software under the terms
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** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: sofa@ukho.gov.uk
** By post: IAU SOFA Center
** HM Nautical Almanac Office
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** United Kingdom
**
**--------------------------------------------------------------------*/
}