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Diffstat (limited to 'ast/erfa/bi00.c')
| -rw-r--r-- | ast/erfa/bi00.c | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/ast/erfa/bi00.c b/ast/erfa/bi00.c new file mode 100644 index 0000000..9000221 --- /dev/null +++ b/ast/erfa/bi00.c @@ -0,0 +1,125 @@ +#include "erfa.h" + +void eraBi00(double *dpsibi, double *depsbi, double *dra) +/* +** - - - - - - - - +** e r a B i 0 0 +** - - - - - - - - +** +** Frame bias components of IAU 2000 precession-nutation models (part +** of MHB2000 with additions). +** +** Returned: +** dpsibi,depsbi double longitude and obliquity corrections +** dra double 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 mean J2000.0 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 9th September 2002 +** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A. +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ +/* The frame bias corrections in longitude and obliquity */ + const double DPBIAS = -0.041775 * ERFA_DAS2R, + DEBIAS = -0.0068192 * ERFA_DAS2R; + +/* The ICRS RA of the J2000.0 equinox (Chapront et al., 2002) */ + const double DRA0 = -0.0146 * ERFA_DAS2R; + + +/* Return the results (which are fixed). */ + *dpsibi = DPBIAS; + *depsbi = DEBIAS; + *dra = DRA0; + + return; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** All rights reserved. +** +** This library is derived, with permission, from the International +** Astronomical Union's "Standards of Fundamental Astronomy" library, +** available from http://www.iausofa.org. +** +** The ERFA version is intended to retain identical functionality to +** the SOFA library, but made distinct through different function and +** file names, as set out in the SOFA license conditions. The SOFA +** original has a role as a reference standard for the IAU and IERS, +** and consequently redistribution is permitted only in its unaltered +** state. The ERFA version is not subject to this restriction and +** therefore can be included in distributions which do not support the +** concept of "read only" software. +** +** Although the intent is to replicate the SOFA API (other than +** replacement of prefix names) and results (with the exception of +** bugs; any that are discovered will be fixed), SOFA is not +** responsible for any errors found in this version of the library. +** +** If you wish to acknowledge the SOFA heritage, please acknowledge +** that you are using a library derived from SOFA, rather than SOFA +** itself. +** +** +** TERMS AND CONDITIONS +** +** Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions +** are met: +** +** 1 Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** +** 2 Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** +** 3 Neither the name of the Standards Of Fundamental Astronomy Board, +** the International Astronomical Union nor the names of its +** contributors may be used to endorse or promote products derived +** from this software without specific prior written permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +** POSSIBILITY OF SUCH DAMAGE. +** +*/ |