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Diffstat (limited to 'ast/pal/palRvlg.c')
-rw-r--r-- | ast/pal/palRvlg.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/ast/pal/palRvlg.c b/ast/pal/palRvlg.c new file mode 100644 index 0000000..255801e --- /dev/null +++ b/ast/pal/palRvlg.c @@ -0,0 +1,106 @@ +/* +*+ +* Name: +* palRvlg + +* Purpose: +* Velocity component in a given direction due to Galactic rotation +* and motion of the local group. + +* Language: +* Starlink ANSI C + +* Type of Module: +* Library routine + +* Invocation: +* double palRvlg( double r2000, double d2000 ) + +* Arguments: +* r2000 = double (Given) +* J2000.0 mean RA (radians) +* d2000 = double (Given) +* J2000.0 mean Dec (radians) + +* Returned Value: +* Component of SOLAR motion in direction R2000,D2000 (km/s). + +* Description: +* This function returns the velocity component in a given +* direction due to the combination of the rotation of the +* Galaxy and the motion of the Galaxy relative to the mean +* motion of the local group. The result is +ve when the Sun +* is receding from the given point on the sky. +* +* Reference: +* - IAU Trans 1976, 168, p201. + +* Authors: +* PTW: Pat Wallace (STFC) +* DSB: David Berry (JAC, Hawaii) +* {enter_new_authors_here} + +* History: +* 2012-02-16 (DSB): +* Initial version. +* Adapted with permission from the Fortran SLALIB library. +* {enter_further_changes_here} + +* Copyright: +* Copyright (C) 1995 Rutherford Appleton Laboratory +* Copyright (C) 2012 Science and Technology Facilities Council. +* 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" + +double palRvlg( double r2000, double d2000 ){ + +/* Local Variables: */ + double vb[ 3 ]; + +/* +* +* Solar velocity due to Galactic rotation and translation +* +* Speed = 300 km/s +* +* Apex = L2,B2 90deg, 0deg +* = RA,Dec 21 12 01.1 +48 19 47 J2000.0 +* +* This is expressed in the form of a J2000.0 x,y,z vector: +* +* VA(1) = X = -SPEED*COS(RA)*COS(DEC) +* VA(2) = Y = -SPEED*SIN(RA)*COS(DEC) +* VA(3) = Z = -SPEED*SIN(DEC) +*/ + + double va[ 3 ] = { -148.23284, +133.44888, -224.09467 }; + +/* Convert given J2000 RA,Dec to x,y,z. */ + eraS2c( r2000, d2000, vb ); + +/* Compute dot product with Solar motion vector. */ + return eraPdp( va, vb ); +} |