| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palEcmat
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| 5 |
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| 6 | * Purpose:
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| 7 | * Form the equatorial to ecliptic rotation matrix - IAU 2006
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| 8 | * precession model.
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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 | * palEcmat( double date, double rmat[3][3] )
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| 18 |
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| 19 | * Arguments:
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| 20 | * date = double (Given)
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| 21 | * TT as Modified Julian Date (JD-2400000.5). The difference
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| 22 | * between TT and TDB is of the order of a millisecond or two
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| 23 | * (i.e. about 0.02 arc-seconds).
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| 24 | * rmat = double[3][3] (Returned)
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| 25 | * Rotation matrix
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| 26 |
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| 27 | * Description:
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| 28 | * The equatorial to ecliptic rotation matrix is found and returned.
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| 29 | * The matrix is in the sense V(ecl) = RMAT * V(equ); the
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| 30 | * equator, equinox and ecliptic are mean of date.
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| 31 |
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| 32 | * Authors:
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| 33 | * PTW: Pat Wallace (STFC)
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| 34 | * DSB: David Berry (JAC, Hawaii)
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| 35 | * {enter_new_authors_here}
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| 36 |
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| 37 | * History:
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| 38 | * 2012-02-10 (DSB):
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| 39 | * Initial version with documentation taken from Fortran SLA
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| 40 | * Adapted with permission from the Fortran SLALIB library.
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| 41 | * {enter_further_changes_here}
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| 42 |
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| 43 | * Copyright:
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| 44 | * Copyright (C) 1996 Rutherford Appleton Laboratory
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| 45 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 46 | * All Rights Reserved.
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| 47 |
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| 48 | * Licence:
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| 49 | * This program is free software: you can redistribute it and/or
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| 50 | * modify it under the terms of the GNU Lesser General Public
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| 51 | * License as published by the Free Software Foundation, either
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| 52 | * version 3 of the License, or (at your option) any later
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| 53 | * version.
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| 54 | *
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| 55 | * This program is distributed in the hope that it will be useful,
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| 56 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 57 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 58 | * GNU Lesser General Public License for more details.
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| 59 | *
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| 60 | * You should have received a copy of the GNU Lesser General
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| 61 | * License along with this program. If not, see
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| 62 | * <http://www.gnu.org/licenses/>.
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| 63 |
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| 64 | * Bugs:
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| 65 | * {note_any_bugs_here}
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| 66 | *-
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| 67 | */
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| 68 |
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| 69 | #include "pal.h"
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| 70 | #include "palmac.h"
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| 71 | #include "pal1sofa.h"
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| 72 |
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| 73 | void palEcmat( double date, double rmat[3][3] ) {
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| 74 |
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| 75 | /* Mean obliquity (the angle between the ecliptic and mean equator of
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| 76 | date). */
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| 77 | double eps0 = eraObl06( PAL__MJD0, date );
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| 78 |
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| 79 | /* Matrix */
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| 80 | palDeuler( "X", eps0, 0.0, 0.0, rmat );
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| 81 |
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| 82 | }
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