#include "erfa.h" void eraC2t00a(double tta, double ttb, double uta, double utb, double xp, double yp, double rc2t[3][3]) /* ** - - - - - - - - - - ** e r a C 2 t 0 0 a ** - - - - - - - - - - ** ** Form the celestial to terrestrial matrix given the date, the UT1 and ** the polar motion, using the IAU 2000A nutation model. ** ** Given: ** tta,ttb double TT as a 2-part Julian Date (Note 1) ** uta,utb double UT1 as a 2-part Julian Date (Note 1) ** xp,yp double coordinates of the pole (radians, Note 2) ** ** Returned: ** rc2t double[3][3] celestial-to-terrestrial matrix (Note 3) ** ** Notes: ** ** 1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates, ** apportioned in any convenient way between the arguments uta and ** utb. For example, JD(UT1)=2450123.7 could be expressed in any of ** these ways, among others: ** ** uta utb ** ** 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. In the case of uta,utb, the ** date & time method is best matched to the Earth rotation angle ** algorithm used: 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) The arguments xp and yp are the coordinates (in radians) of the ** Celestial Intermediate Pole with respect to the International ** Terrestrial Reference System (see IERS Conventions 2003), ** measured along the meridians to 0 and 90 deg west respectively. ** ** 3) The matrix rc2t transforms from celestial to terrestrial ** coordinates: ** ** [TRS] = RPOM * R_3(ERA) * RC2I * [CRS] ** ** = rc2t * [CRS] ** ** where [CRS] is a vector in the Geocentric Celestial Reference ** System and [TRS] is a vector in the International Terrestrial ** Reference System (see IERS Conventions 2003), RC2I is the ** celestial-to-intermediate matrix, ERA is the Earth rotation ** angle and RPOM is the polar motion matrix. ** ** 4) A faster, but slightly less accurate result (about 1 mas), can ** be obtained by using instead the eraC2t00b function. ** ** Called: ** eraC2i00a celestial-to-intermediate matrix, IAU 2000A ** eraEra00 Earth rotation angle, IAU 2000 ** eraSp00 the TIO locator s', IERS 2000 ** eraPom00 polar motion matrix ** eraC2tcio form CIO-based celestial-to-terrestrial matrix ** ** Reference: ** ** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), ** IERS Technical Note No. 32, BKG (2004) ** ** Copyright (C) 2013-2017, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { double rc2i[3][3], era, sp, rpom[3][3]; /* Form the celestial-to-intermediate matrix for this TT (IAU 2000A). */ eraC2i00a(tta, ttb, rc2i ); /* Predict the Earth rotation angle for this UT1. */ era = eraEra00(uta, utb); /* Estimate s'. */ sp = eraSp00(tta, ttb); /* Form the polar motion matrix. */ eraPom00(xp, yp, sp, rpom); /* Combine to form the celestial-to-terrestrial matrix. */ eraC2tcio(rc2i, era, rpom, rc2t); return; } /*---------------------------------------------------------------------- ** ** ** Copyright (C) 2013-2017, 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. ** */