1 /* 2 * - - - - - - - - - - 3 * g a l _ e e 0 0 a 4 * - - - - - - - - - - 5 * 6 * This routine is part of the General Astrodynamics Library 7 * 8 * Description: 9 * 10 * Equation of the equinoxes, compatible with IAU 2000 resolutions. 11 * 12 * This routine is an independent translation of a FORTRAN routine 13 * that is part of IAU's SOFA software collection. 14 * 15 * Status: 16 * 17 * support routine. 18 * 19 * Given: 20 * 21 * date1,date2 d TT as a 2-part Julian Date (Note 1) 22 * 23 * Returned: 24 * 25 * gal_ee00a d equation of the equinoxes (Note 2) 26 * 27 * Notes: 28 * 29 * 1) The TT date date1+date2 is a Julian Date, apportioned in any 30 * convenient way between the two arguments. For example, 31 * JD(TT)=2450123.7 could be expressed in any of these ways, 32 * among others: 33 * 34 * date1 date2 35 * 36 * 2450123.7 0.0 (JD method) 37 * 2451545.0 -1421.3 (J2000 method) 38 * 2400000.5 50123.2 (MJD method) 39 * 2450123.5 0.2 (date & time method) 40 * 41 * The JD method is the most natural and convenient to use in 42 * cases where the loss of several decimal digits of resolution 43 * is acceptable. The J2000 method is best matched to the way 44 * the argument is handled internally and will deliver the 45 * optimum resolution. The MJD method and the date & time methods 46 * are both good compromises between resolution and convenience. 47 * 48 * 2) The result, which is in radians, operates in the following sense: 49 * 50 * Greenwich apparent ST = GMST + equation of the equinoxes 51 * 52 * 3) The result is compatible with the IAU 2000 resolutions. For 53 * further details, see IERS Conventions 2003 and Capitaine et al. 54 * (2002). 55 * 56 * Called: 57 * 58 * gal_pr00 IAU 2000 precession adjustments 59 * gal_obl80 mean obliquity, IAU 1980 60 * gal_nut00a nutation, IAU 2000A 61 * gal_ee00 equation of the equinoxes, IAU 2000 62 * 63 * References: 64 * 65 * Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to 66 * implement the IAU 2000 definition of UT1", Astronomy & 67 * Astrophysics, 406, 1135-1149 (2003) 68 * 69 * McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), 70 * IERS Technical Note No. 32, BKG (2004) 71 * 72 * This revision: 73 * 74 * 2006 November 13 ( c version 2008 January 18 ) 75 * 76 * 77 * Copyright (C) 2008 Paul C. L. Willmott. See notes at end. 78 * 79 *----------------------------------------------------------------------- 80 */ 81 82 #ifndef _GAL_EE00A_H_ 83 #define _GAL_EE00A_H_ 1 84 85 #undef __BEGIN_DECLS 86 #undef __END_DECLS 87 #ifdef __cplusplus 88 #define __BEGIN_DECLS extern "C" { 89 #define __END_DECLS } 90 #else 91 #define __BEGIN_DECLS /* empty */ 92 #define __END_DECLS /* empty */ 93 #endif 94 95 __BEGIN_DECLS 96 97 double 98 gal_ee00a 99 ( 100 double date1, 101 double date2 102 ) ; 103 104 __END_DECLS 105 106 #endif /* !_GAL_EE00A_H_ */ 107 108 /* 109 * gal - General Astrodynamics Library 110 * Copyright (C) 2008 Paul C. L. Willmott 111 * 112 * This program is free software; you can redistribute it and/or modify 113 * it under the terms of the GNU General Public License as published by 114 * the Free Software Foundation; either version 2 of the License, or 115 * (at your option) any later version. 116 * 117 * This program is distributed in the hope that it will be useful, 118 * but WITHOUT ANY WARRANTY; without even the implied warranty of 119 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 120 * GNU General Public License for more details. 121 * 122 * You should have received a copy of the GNU General Public License along 123 * with this program; if not, write to the Free Software Foundation, Inc., 124 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 125 * 126 * Contact: 127 * 128 * Paul Willmott 129 * vp9mu@amsat.org 130 */ 131