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/*
*+
* Name:
* palAmpqk
* Purpose:
* Convert star RA,Dec from geocentric apparent to mean place.
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palAmpqk ( double ra, double da, double amprms[21],
* double *rm, double *dm )
* Arguments:
* ra = double (Given)
* Apparent RA (radians).
* da = double (Given)
* Apparent Dec (radians).
* amprms = double[21] (Given)
* Star-independent mean-to-apparent parameters (see palMappa):
* (0) time interval for proper motion (Julian years)
* (1-3) barycentric position of the Earth (AU)
* (4-6) heliocentric direction of the Earth (unit vector)
* (7) (grav rad Sun)*2/(Sun-Earth distance)
* (8-10) abv: barycentric Earth velocity in units of c
* (11) sqrt(1-v*v) where v=modulus(abv)
* (12-20) precession/nutation (3,3) matrix
* rm = double (Returned)
* Mean RA (radians).
* dm = double (Returned)
* Mean Dec (radians).
* Description:
* Convert star RA,Dec from geocentric apparent to mean place. The "mean"
* coordinate system is in fact close to ICRS. Use of this function
* is appropriate when efficiency is important and where many star
* positions are all to be transformed for one epoch and equinox. The
* star-independent parameters can be obtained by calling the palMappa
* function.
* Note:
* Iterative techniques are used for the aberration and
* light deflection corrections so that the routines
* palAmp (or palAmpqk) and palMap (or palMapqk) are
* accurate inverses; even at the edge of the Sun's disc
* the discrepancy is only about 1 nanoarcsecond.
* Authors:
* PTW: Pat Wallace (STFC)
* TIMJ: Tim Jenness
* {enter_new_authors_here}
* History:
* 2012-02-13 (PTW):
* Initial version.
* Adapted with permission from the Fortran SLALIB library.
* 2016-12-19 (TIMJ):
* Add in light deflection (was missed in the initial port).
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 2000 Rutherford Appleton Laboratory
* Copyright (C) 2012 Science and Technology Facilities Council.
* Copyright (C) 2016 Tim Jenness
* All Rights Reserved.
* Licence:
* This program is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either
* version 3 of the License, or (at your option) any later
* version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "pal1sofa.h"
void palAmpqk ( double ra, double da, double amprms[21], double *rm,
double *dm ){
/* Local Variables: */
double ab1; /* sqrt(1-v*v) where v=modulus of Earth vel */
double abv[3]; /* Earth velocity wrt SSB (c, FK5) */
double p1[3], p2[3], p3[3]; /* work vectors */
double ab1p1, p1dv, p1dvp1, w;
double gr2e, pde, pdep1, ehn[3], p[3];
int i, j;
/* Unpack some of the parameters */
gr2e = amprms[7];
ab1 = amprms[11];
for( i = 0; i < 3; i++ ) {
ehn[i] = amprms[i + 4];
abv[i] = amprms[i + 8];
}
/* Apparent RA,Dec to Cartesian */
eraS2c( ra, da, p3 );
/* Precession and nutation */
eraTrxp( (double(*)[3]) &rms[12], p3, p2 );
/* Aberration */
ab1p1 = ab1 + 1.0;
for( i = 0; i < 3; i++ ) {
p1[i] = p2[i];
}
for( j = 0; j < 2; j++ ) {
p1dv = eraPdp( p1, abv );
p1dvp1 = 1.0 + p1dv;
w = 1.0 + p1dv / ab1p1;
for( i = 0; i < 3; i++ ) {
p1[i] = ( p1dvp1 * p2[i] - w * abv[i] ) / ab1;
}
eraPn( p1, &w, p3 );
for( i = 0; i < 3; i++ ) {
p1[i] = p3[i];
}
}
/* Light deflection */
for( i = 0; i < 3; i++ ) {
p[i] = p1[i];
}
for( j = 0; j < 5; j++ ) {
pde = eraPdp( p, ehn );
pdep1 = 1.0 + pde;
w = pdep1 - gr2e*pde;
for( i = 0; i < 3; i++ ) {
p[i] = (pdep1*p1[i] - gr2e*ehn[i])/w;
}
eraPn( p, &w, p2 );
for( i = 0; i < 3; i++ ) {
p[i] = p2[i];
}
}
/* Mean RA,Dec */
eraC2s( p, rm, dm );
*rm = eraAnp( *rm );
}
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