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 * 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 * (Wallace 2002). * * 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: 2007 October 30 * * Copyright (C) 2008 IAU SOFA Review 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), JD DOUBLE PRECISION DJ0 PARAMETER ( DJ0 = 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-DJ0 ) + DATE2 ) / DJC * Precession rate contributions with respect to IAU 1976/80. DPSIPR = PRECOR * T DEPSPR = OBLCOR * T * 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. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the 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. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "as is" and the Board makes * no warranty as to its use or performance. The Board does not and * cannot warrant the performance or results which the user may * obtain by using the Software. The Board 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 the Board be liable to the user for any consequential, * incidental, or special damages, including any lost profits or lost * savings, even if a Board representative has been advised of such * damages, or for any claim by any third party. * * Correspondence concerning SOFA software should be addressed as * follows: * * Internet email: sofa@rl.ac.uk * Postal address: IAU SOFA Center * Rutherford Appleton Laboratory * Chilton, Didcot, Oxon OX11 0QX * United Kingdom * * *----------------------------------------------------------------------- END