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Diffstat (limited to 'ast/erfa/ltpb.c')
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diff --git a/ast/erfa/ltpb.c b/ast/erfa/ltpb.c new file mode 100644 index 0000000..6818f19 --- /dev/null +++ b/ast/erfa/ltpb.c @@ -0,0 +1,133 @@ +#include "erfa.h" + +void eraLtpb(double epj, double rpb[3][3]) +/* +** - - - - - - - - +** e r a L t p b +** - - - - - - - - +** +** Long-term precession matrix, including ICRS frame bias. +** +** Given: +** epj double Julian epoch (TT) +** +** Returned: +** rpb double[3][3] precession-bias matrix, J2000.0 to date +** +** Notes: +** +** 1) The matrix is in the sense +** +** P_date = rpb x P_ICRS, +** +** where P_ICRS is a vector in the Geocentric Celestial Reference +** System, and P_date is the vector with respect to the Celestial +** Intermediate Reference System at that date but with nutation +** neglected. +** +** 2) A first order frame bias formulation is used, of sub- +** microarcsecond accuracy compared with a full 3D rotation. +** +** 3) The Vondrak et al. (2011, 2012) 400 millennia precession model +** agrees with the IAU 2006 precession at J2000.0 and stays within +** 100 microarcseconds during the 20th and 21st centuries. It is +** accurate to a few arcseconds throughout the historical period, +** worsening to a few tenths of a degree at the end of the +** +/- 200,000 year time span. +** +** References: +** +** Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession +** expressions, valid for long time intervals, Astron.Astrophys. 534, +** A22 +** +** Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession +** expressions, valid for long time intervals (Corrigendum), +** Astron.Astrophys. 541, C1 +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ +/* Frame bias (IERS Conventions 2010, Eqs. 5.21 and 5.33) */ + const double dx = -0.016617 * ERFA_DAS2R, + de = -0.0068192 * ERFA_DAS2R, + dr = -0.0146 * ERFA_DAS2R; + + int i; + double rp[3][3]; + + +/* Precession matrix. */ + eraLtp(epj, rp); + +/* Apply the bias. */ + for ( i = 0; i < 3; i++ ) { + rpb[i][0] = rp[i][0] - rp[i][1]*dr + rp[i][2]*dx; + rpb[i][1] = rp[i][0]*dr + rp[i][1] + rp[i][2]*de; + rpb[i][2] = -rp[i][0]*dx - rp[i][1]*de + rp[i][2]; + } + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |