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author | William Joye <wjoye@cfa.harvard.edu> | 2018-01-09 19:28:07 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2018-01-09 19:28:07 (GMT) |
commit | 3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58 (patch) | |
tree | f278119398ae5d67a6a338705a76db420f6b8f7e /ast/erfa/era00.c | |
parent | 1332d38f2805d986ea130e43218c0d2e870b4dc1 (diff) | |
download | blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.zip blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.gz blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.bz2 |
update ast 8.6.2
Diffstat (limited to 'ast/erfa/era00.c')
-rw-r--r-- | ast/erfa/era00.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/ast/erfa/era00.c b/ast/erfa/era00.c new file mode 100644 index 0000000..01e06f5 --- /dev/null +++ b/ast/erfa/era00.c @@ -0,0 +1,145 @@ +#include "erfa.h" + +double eraEra00(double dj1, double dj2) +/* +** - - - - - - - - - +** e r a E r a 0 0 +** - - - - - - - - - +** +** Earth rotation angle (IAU 2000 model). +** +** Given: +** dj1,dj2 double UT1 as a 2-part Julian Date (see note) +** +** Returned (function value): +** double Earth rotation angle (radians), range 0-2pi +** +** Notes: +** +** 1) The UT1 date dj1+dj2 is a Julian Date, apportioned in any +** convenient way between the arguments dj1 and dj2. For example, +** JD(UT1)=2450123.7 could be expressed in any of these ways, +** among others: +** +** dj1 dj2 +** +** 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 and MJD methods are good compromises +** between resolution and convenience. The date & time method is +** best matched to the algorithm used: maximum precision is +** delivered when the dj1 argument is for 0hrs UT1 on the day in +** question and the dj2 argument lies in the range 0 to 1, or vice +** versa. +** +** 2) The algorithm is adapted from Expression 22 of Capitaine et al. +** 2000. The time argument has been expressed in days directly, +** and, to retain precision, integer contributions have been +** eliminated. The same formulation is given in IERS Conventions +** (2003), Chap. 5, Eq. 14. +** +** Called: +** eraAnp normalize angle into range 0 to 2pi +** +** References: +** +** Capitaine N., Guinot B. and McCarthy D.D, 2000, Astron. +** Astrophys., 355, 398-405. +** +** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), +** IERS Technical Note No. 32, BKG (2004) +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double d1, d2, t, f, theta; + + +/* Days since fundamental epoch. */ + if (dj1 < dj2) { + d1 = dj1; + d2 = dj2; + } else { + d1 = dj2; + d2 = dj1; + } + t = d1 + (d2- ERFA_DJ00); + +/* Fractional part of T (days). */ + f = fmod(d1, 1.0) + fmod(d2, 1.0); + +/* Earth rotation angle at this UT1. */ + theta = eraAnp(ERFA_D2PI * (f + 0.7790572732640 + + 0.00273781191135448 * t)); + + return theta; + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |