SUBROUTINE iau_PR00 ( DATE1, DATE2, DPSIPR, DEPSPR ) *+ * - - - - - - - - - * i a u _ P R 0 0 * - - - - - - - - - * * Precession-rate part of the IAU 2000 precession-nutation models * (part of MHB2000). * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: canonical model. * * Given: * DATE1,DATE2 d TT as a 2-part Julian Date (Note 1) * * Returned: * DPSIPR,DEPSPR d precession corrections (Notes 2,3) * * 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 precession adjustments are expressed as "nutation components", * corrections in longitude and obliquity with respect to the J2000.0 * equinox and ecliptic. * * 3) Although the precession adjustments are stated to be with respect * to Lieske et al. (1977), the MHB2000 model does not specify which * set of Euler angles are to be used and how the adjustments are to * be applied. The most literal and straightforward procedure is to * adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and * to add DPSIPR to psi_A and DEPSPR to both omega_A and eps_A. * * 4) This is an implementation of one aspect of the IAU 2000A nutation * model, formally adopted by the IAU General Assembly in 2000, * namely MHB2000 (Mathews et al. 2002). * * References: * * Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions * for the precession quantities based upon the IAU (1976) System of * Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977) * * Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation * and precession New nutation series for nonrigid Earth and * insights into the Earth's interior", J.Geophys.Res., 107, B4, * 2002. The MHB2000 code itself was obtained on 9th September 2002 * from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A. * * Wallace, P.T., "Software for Implementing the IAU 2000 * Resolutions", in IERS Workshop 5.1 (2002). * * This revision: 2009 December 15 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION DATE1, DATE2, DPSIPR, DEPSPR * Arcseconds to radians DOUBLE PRECISION DAS2R PARAMETER ( DAS2R = 4.848136811095359935899141D-6 ) * Reference epoch (J2000.0), JD DOUBLE PRECISION DJ00 PARAMETER ( DJ00 = 2451545D0 ) * Days per Julian century DOUBLE PRECISION DJC PARAMETER ( DJC = 36525D0 ) DOUBLE PRECISION T * ------------------------------------ * Precession and obliquity corrections (radians per century) * ------------------------------------ DOUBLE PRECISION PRECOR, OBLCOR PARAMETER ( PRECOR = -0.29965D0 * DAS2R, : OBLCOR = -0.02524D0 * DAS2R ) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Interval between fundamental epoch J2000.0 and given date (JC). T = ( ( DATE1-DJ00 ) + DATE2 ) / DJC * Precession rate contributions with respect to IAU 1976/80. DPSIPR = PRECOR * T DEPSPR = OBLCOR * T * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2023 * Standards of Fundamental Astronomy Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND * CONDITIONS WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Board ("SOFA"). * * 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 distribute SOFA source code to others, * and use and adapt its code and algorithms in your own software, * on a world-wide, royalty-free basis. That portion of your * distribution that does not consist of intact and unchanged copies * of SOFA source code files is a "derived work" that must comply * 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 itself constitute software provided by and/or * endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon, contains and/or differs * from the original SOFA software. * * c) The names of all routines in your derived work shall not * include the prefix "iau" or "sofa" or trivial modifications * thereof such as changes of case. * * d) 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. * * e) 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. * * Note that, as originally distributed, the SOFA software is * intended to be a definitive implementation of the IAU standards, * and consequently third-party modifications are discouraged. All * variations, no matter how minor, must be explicitly marked as * such, as explained above. * * 4. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or * by inappropriate modification. * * 5. The SOFA software is provided "as is" and SOFA makes no warranty * as to its use or performance. SOFA does not and cannot warrant * the performance or results which the user may obtain by using the * SOFA software. SOFA makes no warranties, express or implied, as * to non-infringement of third party rights, merchantability, or * fitness for any particular purpose. In no event will SOFA be * liable to the user for any consequential, incidental, or special * damages, including any lost profits or lost savings, even if a * SOFA representative has been advised of such damages, or for any * claim by any third party. * * 6. The provision of any version of the SOFA software under the terms * and conditions specified herein does not imply that future * versions will also be made available under the same terms and * conditions. * * In any published work or commercial product which uses the SOFA * software directly, acknowledgement (see www.iausofa.org) is * appreciated. * * Correspondence concerning SOFA software should be addressed as * follows: * * By email: sofa@ukho.gov.uk * By post: IAU SOFA Center * HM Nautical Almanac Office * UK Hydrographic Office * Admiralty Way, Taunton * Somerset, TA1 2DN * United Kingdom * *----------------------------------------------------------------------- END