SUBROUTINE iau_BI00 ( DPSIBI, DEPSBI, DRA ) *+ * - - - - - - - - - * i a u _ B I 0 0 * - - - - - - - - - * * Frame bias components of IAU 2000 precession-nutation models; part * of the Mathews-Herring-Buffett (MHB2000) nutation series, with * additions. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: canonical model. * * Returned: * DPSIBI,DEPSBI d longitude and obliquity corrections * DRA d the ICRS RA of the J2000.0 mean equinox * * Notes: * * 1) The frame bias corrections in longitude and obliquity (radians) * are required in order to correct for the offset between the GCRS * pole and the J2000.0 mean pole. They define, with respect to the * GCRS frame, a J2000.0 mean pole that is consistent with the rest * of the IAU 2000A precession-nutation model. * * 2) In addition to the displacement of the pole, the complete * description of the frame bias requires also an offset in right * ascension. This is not part of the IAU 2000A model, and is from * Chapront et al. (2002). It is returned in radians. * * 3) This is a supplemented 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: * * Chapront, J., Chapront-Touze, M. & Francou, G., Astron.Astrophys., * 387, 700, 2002. * * 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 2002 September 9 * from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A. * * This revision: 2020 October 29 * * SOFA release 2021-05-12 * * Copyright (C) 2021 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION DPSIBI, DEPSBI, DRA * Arcseconds to radians DOUBLE PRECISION DAS2R PARAMETER ( DAS2R = 4.848136811095359935899141D-6 ) * The frame bias corrections in longitude and obliquity DOUBLE PRECISION DPBIAS, DEBIAS PARAMETER ( DPBIAS = -0.041775D0 * DAS2R, : DEBIAS = -0.0068192D0 * DAS2R ) * The ICRS RA of the J2000.0 equinox (Chapront et al., 2002) DOUBLE PRECISION DRA0 PARAMETER ( DRA0 = -0.0146D0 * DAS2R ) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Return the results (which are fixed). DPSIBI = DPBIAS DEPSBI = DEBIAS DRA = DRA0 * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2021 * 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. 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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