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Diffstat (limited to 'ast/erfa/ecm06.c')
| -rw-r--r-- | ast/erfa/ecm06.c | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/ast/erfa/ecm06.c b/ast/erfa/ecm06.c new file mode 100644 index 0000000..ce19ba2 --- /dev/null +++ b/ast/erfa/ecm06.c @@ -0,0 +1,144 @@ +#include "erfa.h" + +void eraEcm06(double date1, double date2, double rm[3][3]) +/* +** - - - - - - - - - +** e r a E c m 0 6 +** - - - - - - - - - +** +** ICRS equatorial to ecliptic rotation matrix, IAU 2006. +** +** Given: +** date1,date2 double TT as a 2-part Julian date (Note 1) +** +** Returned: +** rm double[3][3] ICRS to ecliptic rotation matrix +** +** 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. +** +** 1) The matrix is in the sense +** +** E_ep = rm x P_ICRS, +** +** where P_ICRS is a vector with respect to ICRS right ascension +** and declination axes and E_ep is the same vector with respect to +** the (inertial) ecliptic and equinox of date. +** +** 2) P_ICRS is a free vector, merely a direction, typically of unit +** magnitude, and not bound to any particular spatial origin, such +** as the Earth, Sun or SSB. No assumptions are made about whether +** it represents starlight and embodies astrometric effects such as +** parallax or aberration. The transformation is approximately that +** between mean J2000.0 right ascension and declination and ecliptic +** longitude and latitude, with only frame bias (always less than +** 25 mas) to disturb this classical picture. +** +** Called: +** eraObl06 mean obliquity, IAU 2006 +** eraPmat06 PB matrix, IAU 2006 +** eraIr initialize r-matrix to identity +** eraRx rotate around X-axis +** eraRxr product of two r-matrices +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double ob, bp[3][3], e[3][3]; + + +/* Obliquity, IAU 2006. */ + ob = eraObl06(date1, date2); + +/* Precession-bias matrix, IAU 2006. */ + eraPmat06(date1, date2, bp); + +/* Equatorial of date to ecliptic matrix. */ + eraIr(e); + eraRx(ob, e); + +/* ICRS to ecliptic coordinates rotation matrix, IAU 2006. */ + eraRxr(e, bp, rm); + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |