SUBROUTINE iau_APCI13 ( DATE1, DATE2, ASTROM, EO )
*+
* - - - - - - - - - - -
* i a u _ A P C I 1 3
* - - - - - - - - - - -
*
* For a terrestrial observer, prepare star-independent astrometry
* parameters for transformations between ICRS and geocentric CIRS
* coordinates. The caller supplies the date, and SOFA models are
* used to predict the Earth ephemeris and CIP/CIO.
*
* The parameters produced by this routine are required in the parallax,
* light deflection, aberration, and bias-precession-nutation parts of
* the astrometric transformation chain.
*
* This routine is part of the International Astronomical Union's
* SOFA (Standards of Fundamental Astronomy) software collection.
*
* Status: support routine.
*
* Given:
* DATE1 d TDB as a 2-part...
* DATE2 d ...Julian Date (Note 1)
*
* Returned:
* ASTROM d(30) star-independent astrometry parameters:
* (1) PM time interval (SSB, Julian years)
* (2-4) SSB to observer (vector, au)
* (5-7) Sun to observer (unit vector)
* (8) distance from Sun to observer (au)
* (9-11) v: barycentric observer velocity (vector, c)
* (12) sqrt(1-|v|^2): reciprocal of Lorenz factor
* (13-21) bias-precession-nutation matrix
* (22) unchanged
* (23) unchanged
* (24) unchanged
* (25) unchanged
* (26) unchanged
* (27) unchanged
* (28) unchanged
* (29) unchanged
* (30) unchanged
* EO d equation of the origins (ERA-GST)
*
* 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
*
* 2450123.7D0 0D0 (JD method)
* 2451545D0 -1421.3D0 (J2000 method)
* 2400000.5D0 50123.2D0 (MJD method)
* 2450123.5D0 0.2D0 (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 routine 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 and CIP/CIO, the routine iau_APCI can be used instead of
* the present routine.
*
* 4) This is one of several routines that inserts into the ASTROM
* array star-independent parameters needed for the chain of
* astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
*
* The various routines support different classes of observer and
* portions of the transformation chain:
*
* routines observer transformation
*
* iau_APCG iau_APCG13 geocentric ICRS <-> GCRS
* iau_APCI iau_APCI13 terrestrial ICRS <-> CIRS
* iau_APCO iau_APCO13 terrestrial ICRS <-> observed
* iau_APCS iau_APCS13 space ICRS <-> GCRS
* iau_APER iau_APER13 terrestrial update Earth rotation
* iau_APIO iau_APIO13 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 array ASTROM produced by this routine is used by
* iau_ATCIQ* and iau_ATICQ*.
*
* Called:
* iau_EPV00 Earth position and velocity
* iau_PNM06A classical NPB matrix, IAU 2006/2000A
* iau_BPN2XY extract CIP X,Y coordinates from NPB matrix
* iau_S06 the CIO locator s, given X,Y, IAU 2006
* iau_APCI astrometry parameters, ICRS-CIRS
* iau_EORS equation of the origins, given NPB matrix and s
*
* This revision: 2017 March 12
*
* SOFA release 2021-05-12
*
* Copyright (C) 2021 IAU SOFA Board. See notes at end.
*
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION DATE1, DATE2, ASTROM(30), EO
INTEGER J
DOUBLE PRECISION PVH(3,2), PVB(3,2), R(3,3), X, Y, S
DOUBLE PRECISION iau_S06, iau_EORS
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* Earth barycentric & heliocentric position/velocity (au, au/d).
CALL iau_EPV00 ( DATE1, DATE2, PVH, PVB, J )
* Form the equinox based BPN matrix, IAU 2006/2000A.
CALL iau_PNM06A ( DATE1, DATE2, R )
* Extract CIP X,Y.
CALL iau_BPN2XY ( R, X, Y )
* Obtain CIO locator s.
S = iau_S06 ( DATE1, DATE2, X, Y )
* Compute the star-independent astrometry parameters.
CALL iau_APCI ( DATE1, DATE2, PVB, PVH, X, Y, S, ASTROM )
* Equation of the origins.
EO = iau_EORS ( R, S )
* 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
* original software, nor file a patent application for SOFA
* software or algorithms embedded in the SOFA software.
*
* e) These requirements must be reproduced intact in any source
* distribution and shall apply to anyone to whom you have
* granted a further right to modify the source code of your
* derived work.
*
* 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
* disrepute, either by misuse, or use for inappropriate tasks, or
* by inappropriate modification.
*
* 5. The SOFA software is provided "as is" and SOFA makes no warranty
* as to its use or performance. SOFA does not and cannot warrant
* the performance or results which the user may obtain by using the
* SOFA software. SOFA makes no warranties, express or implied, as
* to non-infringement of third party rights, merchantability, or
* fitness for any particular purpose. In no event will SOFA be
* liable to the user for any consequential, incidental, or special
* damages, including any lost profits or lost savings, even if a
* SOFA representative has been advised of such damages, or for any
* claim by any third party.
*
* 6. The provision of any version of the SOFA software under the terms
* and conditions specified herein does not imply that future
* 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
* UK Hydrographic Office
* Admiralty Way, Taunton
* Somerset, TA1 2DN
* United Kingdom
*
*-----------------------------------------------------------------------
END