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Diffstat (limited to 'ast/erfa/pr00.c')
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diff --git a/ast/erfa/pr00.c b/ast/erfa/pr00.c new file mode 100644 index 0000000..3477ad3 --- /dev/null +++ b/ast/erfa/pr00.c @@ -0,0 +1,151 @@ +#include "erfa.h" + +void eraPr00(double date1, double date2, double *dpsipr, double *depspr) +/* +** - - - - - - - - +** e r a P r 0 0 +** - - - - - - - - +** +** Precession-rate part of the IAU 2000 precession-nutation models +** (part of MHB2000). +** +** Given: +** date1,date2 double TT as a 2-part Julian Date (Note 1) +** +** Returned: +** dpsipr,depspr double 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 +** +** 2450123.7 0.0 (JD method) +** 2451545.0 -1421.3 (J2000 method) +** 2400000.5 50123.2 (MJD method) +** 2450123.5 0.2 (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). +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double t; + +/* Precession and obliquity corrections (radians per century) */ + static const double PRECOR = -0.29965 * ERFA_DAS2R, + OBLCOR = -0.02524 * ERFA_DAS2R; + + +/* Interval between fundamental epoch J2000.0 and given date (JC). */ + t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC; + +/* Precession rate contributions with respect to IAU 1976/80. */ + *dpsipr = PRECOR * t; + *depspr = OBLCOR * t; + + return; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2014, 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. +** +*/ |