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Diffstat (limited to 'ast/erfa/nut06a.c')
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diff --git a/ast/erfa/nut06a.c b/ast/erfa/nut06a.c new file mode 100644 index 0000000..c4d945e --- /dev/null +++ b/ast/erfa/nut06a.c @@ -0,0 +1,162 @@ +#include "erfa.h" + +void eraNut06a(double date1, double date2, double *dpsi, double *deps) +/* +** - - - - - - - - - - +** e r a N u t 0 6 a +** - - - - - - - - - - +** +** IAU 2000A nutation with adjustments to match the IAU 2006 +** precession. +** +** Given: +** date1,date2 double TT as a 2-part Julian Date (Note 1) +** +** Returned: +** dpsi,deps double nutation, luni-solar + planetary (Note 2) +** +** 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 nutation components in longitude and obliquity are in radians +** and with respect to the mean equinox and ecliptic of date, +** IAU 2006 precession model (Hilton et al. 2006, Capitaine et al. +** 2005). +** +** 3) The function first computes the IAU 2000A nutation, then applies +** adjustments for (i) the consequences of the change in obliquity +** from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the +** secular variation in the Earth's dynamical form factor J2. +** +** 4) The present function provides classical nutation, complementing +** the IAU 2000 frame bias and IAU 2006 precession. It delivers a +** pole which is at current epochs accurate to a few tens of +** microarcseconds, apart from the free core nutation. +** +** Called: +** eraNut00a nutation, IAU 2000A +** +** References: +** +** Chapront, J., Chapront-Touze, M. & Francou, G. 2002, +** Astron.Astrophys. 387, 700 +** +** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977, +** Astron.Astrophys. 58, 1-16 +** +** Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res. +** 107, B4. The MHB_2000 code itself was obtained on 9th September +** 2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A. +** +** Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M., +** Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683 +** +** Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999, +** Astron.Astrophys.Supp.Ser. 135, 111 +** +** Wallace, P.T., "Software for Implementing the IAU 2000 +** Resolutions", in IERS Workshop 5.1 (2002) +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double t, fj2, dp, de; + + +/* Interval between fundamental date J2000.0 and given date (JC). */ + t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC; + +/* Factor correcting for secular variation of J2. */ + fj2 = -2.7774e-6 * t; + +/* Obtain IAU 2000A nutation. */ + eraNut00a(date1, date2, &dp, &de); + +/* Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5). */ + *dpsi = dp + dp * (0.4697e-6 + fj2); + *deps = de + de * fj2; + + 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. +** +*/ |