SUBROUTINE iau_NUT06A ( DATE1, DATE2, DPSI, DEPS ) *+ * - - - - - - - - - - - * i a u _ N U T 0 6 A * - - - - - - - - - - - * * IAU 2000A nutation with adjustments to match the IAU 2006 precession. * * Given: * DATE1,DATE2 d TT as a 2-part Julian Date (Note 1) * * Returned: * DPSI,DEPS d nutation, luni-solar + planetary (Note 2) * * Status: canonical model. * * Notes: * * 1) The TT date DATE1+DATE2 is a Julian Date, apportioned in any * convenient way between the two arguments. For example, * JD(TT)=2450123.7 could be expressed in any of these ways, * among others * * DATE1 DATE2 * * 2450123.7D0 0D0 (JD method) * 2451545D0 -1421.3D0 (J2000 method) * 2400000.5D0 50123.2D0 (MJD method) * 2450123.5D0 0.2D0 (date & time method) * * The JD method is the most natural and convenient to use in * cases where the loss of several decimal digits of resolution * is acceptable. The J2000 method is best matched to the way * the argument is handled internally and will deliver the * optimum resolution. The MJD method and the date & time methods * are both good compromises between resolution and convenience. * * 2) The nutation components in longitude and obliquity are in radians * and with respect to the mean equinox and ecliptic of date, * IAU 2006 precession model (Hilton et al. 2006, Capitaine et al. * 2005). * * 3) The routine first computes the IAU 2000A nutation, then applies * adjustments for (i) the consequences of the change in obliquity * from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the * secular variation in the Earth's dynamical flattening. * * 4) The present routine provides classical nutation, complementing * the IAU 2000 frame bias and IAU 2006 precession. It delivers a * pole which is at current epochs accurate to a few tens of * microarcseconds, apart from the free core nutation. * * Called: * iau_NUT00A nutation, IAU 2000A * * Reference: * * Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981 * * This revision: 2008 May 24 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION DATE1, DATE2, DPSI, DEPS * Reference epoch (J2000), JD DOUBLE PRECISION DJ00 PARAMETER ( DJ00 = 2451545D0 ) * Days per Julian century DOUBLE PRECISION DJC PARAMETER ( DJC = 36525D0 ) * Miscellaneous DOUBLE PRECISION T, FJ2, DP, DE * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Interval between fundamental date J2000.0 and given date (JC). T = ( ( DATE1-DJ00 ) + DATE2 ) / DJC * Factor correcting for secular variation of J2. FJ2 = -2.7774D-6 * T * Obtain IAU 2000A nutation. CALL iau_NUT00A ( DATE1, DATE2, DP, DE ) * Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5). DPSI = DP + DP * ( 0.4697D-6 + FJ2 ) DEPS = DE + DE * FJ2 * Finished. *+----------------------------------------------------------------------- * * Copyright (C) 2008 * Standards Of Fundamental Astronomy Review Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS * WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Review Board ("the Board"). * * 2. Permission is granted to anyone to use the SOFA software for any * purpose, including commercial applications, free of charge and * without payment of royalties, subject to the conditions and * restrictions listed below. * * 3. You (the user) may copy and adapt the SOFA software and its * algorithms for your own purposes and you may copy and distribute * a resulting "derived work" to others on a world-wide, royalty-free * basis, provided that the derived work complies with the following * requirements: * * a) Your work shall be marked or carry a statement that it (i) uses * routines and computations derived by you from software provided * by SOFA under license to you; and (ii) does not contain * software provided by SOFA or software that has been distributed * by or endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon and/or differs from the * original SOFA software. * * c) The name(s) of all routine(s) that you distribute shall differ * from the SOFA names, even when the SOFA content has not been * otherwise changed. * * d) The routine-naming prefix "iau" shall not be used. * * e) The origin of the SOFA components of your derived work must not * be misrepresented; you must not claim that you wrote the * original software, nor file a patent application for SOFA * software or algorithms embedded in the SOFA software. * * f) These requirements must be reproduced intact in any source * distribution and shall apply to anyone to whom you have granted * a further right to modify the source code of your derived work. * * 4. 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