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Diffstat (limited to 'ast/pal/palAmpqk.c')
-rw-r--r-- | ast/pal/palAmpqk.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/ast/pal/palAmpqk.c b/ast/pal/palAmpqk.c new file mode 100644 index 0000000..ce698b8 --- /dev/null +++ b/ast/pal/palAmpqk.c @@ -0,0 +1,159 @@ +/* +*+ +* 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 ); +} |