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Diffstat (limited to 'ast/erfa/gmst06.c')
| -rw-r--r-- | ast/erfa/gmst06.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/ast/erfa/gmst06.c b/ast/erfa/gmst06.c new file mode 100644 index 0000000..2fcb1a5 --- /dev/null +++ b/ast/erfa/gmst06.c @@ -0,0 +1,145 @@ +#include "erfa.h" + +double eraGmst06(double uta, double utb, double tta, double ttb) +/* +** - - - - - - - - - - +** e r a G m s t 0 6 +** - - - - - - - - - - +** +** Greenwich mean sidereal time (consistent with IAU 2006 precession). +** +** Given: +** uta,utb double UT1 as a 2-part Julian Date (Notes 1,2) +** tta,ttb double TT as a 2-part Julian Date (Notes 1,2) +** +** Returned (function value): +** double Greenwich mean sidereal time (radians) +** +** Notes: +** +** 1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both +** Julian Dates, apportioned in any convenient way between the +** argument pairs. For example, JD=2450123.7 could be expressed in +** any of these ways, among others: +** +** Part A Part B +** +** 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 (in the case of UT; the TT is not at all critical +** in this respect). The J2000 and MJD methods are good compromises +** between resolution and convenience. For UT, the date & time +** method is best matched to the algorithm that is used by the Earth +** rotation angle function, called internally: maximum precision is +** delivered when the uta argument is for 0hrs UT1 on the day in +** question and the utb argument lies in the range 0 to 1, or vice +** versa. +** +** 2) Both UT1 and TT are required, UT1 to predict the Earth rotation +** and TT to predict the effects of precession. If UT1 is used for +** both purposes, errors of order 100 microarcseconds result. +** +** 3) This GMST is compatible with the IAU 2006 precession and must not +** be used with other precession models. +** +** 4) The result is returned in the range 0 to 2pi. +** +** Called: +** eraEra00 Earth rotation angle, IAU 2000 +** eraAnp normalize angle into range 0 to 2pi +** +** Reference: +** +** Capitaine, N., Wallace, P.T. & Chapront, J., 2005, +** Astron.Astrophys. 432, 355 +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double t, gmst; + + +/* TT Julian centuries since J2000.0. */ + t = ((tta - ERFA_DJ00) + ttb) / ERFA_DJC; + +/* Greenwich mean sidereal time, IAU 2006. */ + gmst = eraAnp(eraEra00(uta, utb) + + ( 0.014506 + + ( 4612.156534 + + ( 1.3915817 + + ( -0.00000044 + + ( -0.000029956 + + ( -0.0000000368 ) + * t) * t) * t) * t) * t) * ERFA_DAS2R); + + return gmst; + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |