| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palEvp
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| 5 |
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| 6 | * Purpose:
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| 7 | * Returns the barycentric and heliocentric velocity and position of the
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| 8 | * Earth.
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| 9 |
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| 10 | * Language:
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| 11 | * Starlink ANSI C
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| 12 |
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| 13 | * Type of Module:
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| 14 | * Library routine
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| 15 |
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| 16 | * Invocation:
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| 17 | * void palEvp( double date, double deqx, double dvb[3], double dpb[3],
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| 18 | * double dvh[3], double dph[3] )
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| 19 |
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| 20 | * Arguments:
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| 21 | * date = double (Given)
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| 22 | * TDB (loosely ET) as a Modified Julian Date (JD-2400000.5)
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| 23 | * deqx = double (Given)
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| 24 | * Julian epoch (e.g. 2000.0) of mean equator and equinox of the
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| 25 | * vectors returned. If deqx <= 0.0, all vectors are referred to the
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| 26 | * mean equator and equinox (FK5) of epoch date.
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| 27 | * dvb = double[3] (Returned)
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| 28 | * Barycentric velocity (AU/s, AU)
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| 29 | * dpb = double[3] (Returned)
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| 30 | * Barycentric position (AU/s, AU)
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| 31 | * dvh = double[3] (Returned)
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| 32 | * heliocentric velocity (AU/s, AU)
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| 33 | * dph = double[3] (Returned)
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| 34 | * Heliocentric position (AU/s, AU)
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| 35 |
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| 36 | * Description:
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| 37 | * Returns the barycentric and heliocentric velocity and position of the
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| 38 | * Earth at a given epoch, given with respect to a specified equinox.
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| 39 | * For information about accuracy, see the function eraEpv00.
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| 40 |
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| 41 | * Authors:
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| 42 | * PTW: Pat Wallace (STFC)
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| 43 | * {enter_new_authors_here}
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| 44 |
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| 45 | * History:
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| 46 | * 2012-02-13 (PTW):
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| 47 | * Initial version.
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| 48 | * Adapted with permission from the Fortran SLALIB library.
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| 49 | * {enter_further_changes_here}
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| 50 |
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| 51 | * Copyright:
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| 52 | * Copyright (C) 2005 Patrick T. Wallace
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| 53 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 54 | * All Rights Reserved.
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| 55 |
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| 56 | * Licence:
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| 57 | * This program is free software: you can redistribute it and/or
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| 58 | * modify it under the terms of the GNU Lesser General Public
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| 59 | * License as published by the Free Software Foundation, either
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| 60 | * version 3 of the License, or (at your option) any later
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| 61 | * version.
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| 62 | *
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| 63 | * This program is distributed in the hope that it will be useful,
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| 64 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 65 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 66 | * GNU Lesser General Public License for more details.
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| 67 | *
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| 68 | * You should have received a copy of the GNU Lesser General
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| 69 | * License along with this program. If not, see
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| 70 | * <http://www.gnu.org/licenses/>.
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| 71 |
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| 72 | * Bugs:
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| 73 | * {note_any_bugs_here}
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| 74 | *-
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| 75 | */
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| 76 |
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| 77 | #include "pal.h"
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| 78 | #include "palmac.h"
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| 79 | #include "pal1sofa.h"
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| 80 |
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| 81 | void palEvp( double date, double deqx, double dvb[3], double dpb[3],
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| 82 | double dvh[3], double dph[3] ){
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| 83 |
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| 84 | /* Local Variables; */
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| 85 | int i;
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| 86 | double pvh[2][3], pvb[2][3], d1, d2, r[3][3];
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| 87 |
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| 88 | /* BCRS PV-vectors. */
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| 89 | eraEpv00 ( 2400000.5, date, pvh, pvb );
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| 90 |
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| 91 | /* Was precession to another equinox requested? */
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| 92 | if ( deqx > 0.0 ) {
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| 93 |
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| 94 | /* Yes: compute precession matrix from J2000.0 to deqx. */
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| 95 | eraEpj2jd ( deqx, &d1, &d2 );
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| 96 | eraPmat06 ( d1, d2, r );
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| 97 |
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| 98 | /* Rotate the PV-vectors. */
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| 99 | eraRxpv ( r, pvh, pvh );
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| 100 | eraRxpv ( r, pvb, pvb );
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| 101 | }
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| 102 |
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| 103 | /* Return the required vectors. */
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| 104 | for ( i = 0; i < 3; i++ ) {
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| 105 | dvh[i] = pvh[1][i] / PAL__SPD;
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| 106 | dvb[i] = pvb[1][i] / PAL__SPD;
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| 107 | dph[i] = pvh[0][i];
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| 108 | dpb[i] = pvb[0][i];
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| 109 | }
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| 110 | }
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