src/Marando/IAU/iauAtic13.php
public static function Atic13($ri, $di, $date1, $date2, &$rc, &$dc, &$eo) {
    /* Star-independent astrometry parameters */
    $astrom = new iauASTROM();

    /* Star-independent astrometry parameters. */
    IAU::Apci13($date1, $date2, $astrom, $eo);

    /* CIRS to ICRS astrometric. */
    IAU::Aticq($ri, $di, $astrom, $rc, $dc);

    /* Finished. */
  }
public static function Atic13($ri, $di, $date1, $date2, &$rc, &$dc, &$eo) {
    /* Star-independent astrometry parameters */
    $astrom = new iauASTROM();

    /* Star-independent astrometry parameters. */
    IAU::Apci13($date1, $date2, $astrom, $eo);

    /* CIRS to ICRS astrometric. */
    IAU::Aticq($ri, $di, $astrom, $rc, $dc);

    /* Finished. */
  }
public static function Atic13 ( $ ri , $ di , $ date1 , $ date2 , & $ rc , & $ dc , & $ eo ) { /* Star-independent astrometry parameters */ $ astrom = new iauASTROM ( ) ; /* Star-independent astrometry parameters. */ IAU :: Apci13 ( $ date1 , $ date2 , $ astrom , $ eo ) ; /* CIRS to ICRS astrometric. */ IAU :: Aticq ( $ ri , $ di , $ astrom , $ rc , $ dc ) ; /* Finished. */ }
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Transform star RA,Dec from geocentric CIRS to ICRS astrometric.

This function is part of the International Astronomical Union's
SOFA (Standards of Fundamental Astronomy) software collection.

Status:  support function.

Given:
ri,di  double  CIRS geocentric RA,Dec (radians)
date1  double  TDB as a 2-part...
date2  double  ...Julian Date (Note 1)

Returned:
rc,dc  double  ICRS astrometric RA,Dec (radians)
eo     double  equation of the origins (ERA-GST, Note 4)

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) Iterative techniques are used for the aberration and light
deflection corrections so that the functions iauAtic13 (or
iauAticq) and iauAtci13 (or iauAtciq) are accurate inverses;
even at the edge of the Sun's disk the discrepancy is only about
1 nanoarcsecond.

3) The available accuracy is better than 1 milliarcsecond, limited
mainly by the precession-nutation model that is used, namely
IAU 2000A/2006.  Very close to solar system bodies, additional
errors of up to several milliarcseconds can occur because of
unmodeled light deflection;  however, the Sun's contribution is
taken into account, to first order.  The accuracy limitations of
the SOFA function iauEpv00 (used to compute Earth position and
velocity) can contribute aberration errors of up to
5 microarcseconds.  Light deflection at the Sun's limb is
uncertain at the 0.4 mas level.

4) Should the transformation to (equinox based) J2000.0 mean place
be required rather than (CIO based) ICRS coordinates, subtract the
equation of the origins from the returned right ascension:
RA = RI - EO.  (The iauAnp function can then be applied, as
required, to keep the result in the conventional 0-2pi range.)

Called:
iauApci13    astrometry parameters, ICRS-CIRS, 2013
iauAticq     quick CIRS to ICRS astrometric

This revision:   2013 October 9

SOFA release 2015-02-09

Copyright (C) 2015 IAU SOFA Board.  See notes at end.
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