SUBROUTINE iau_C2T00A ( TTA, TTB, UTA, UTB, XP, YP, RC2T ) *+ * - - - - - - - - - - - * i a u _ 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. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * TTA,TTB d TT as a 2-part Julian Date (Note 1) * UTA,UTB d UT1 as a 2-part Julian Date (Note 1) * XP,YP d coordinates of the pole (radians, Note 2) * * Returned: * RC2T d(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 * * 2450123.7D0 0D0 (JD method) * 2451545D0 -1421.3D0 (J2000 method) * 2400000.5D0 50123.2D0 (MJD method) * 2450123.5D0 0.2D0 (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 accuracy (or, at least, minimum noise) 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) XP and YP are the "coordinates of the pole", in radians, which * position the Celestial Intermediate Pole in the International * Terrestrial Reference System (see IERS Conventions 2003). In a * geocentric right-handed triad u,v,w, where the w-axis points at * the north geographic pole, the v-axis points towards the origin * of longitudes and the u axis completes the system, XP = +u and * YP = -v. * * 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 iau_C2T00B routine. * * Called: * iau_C2I00A celestial-to-intermediate matrix, IAU 2000A * iau_ERA00 Earth rotation angle, IAU 2000 * iau_SP00 the TIO locator s', IERS 2000 * iau_POM00 polar motion matrix * iau_C2TCIO form CIO-based celestial-to-terrestrial matrix * * Reference: * * McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), * IERS Technical Note No. 32, BKG (2004) * * This revision: 2007 May 9 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION TTA, TTB, UTA, UTB, XP, YP, RC2T(3,3) DOUBLE PRECISION RC2I(3,3), ERA, SP, RPOM(3,3) DOUBLE PRECISION iau_ERA00, iau_SP00 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Form the celestial-to-intermediate matrix for this TT (IAU 2000A). CALL iau_C2I00A ( TTA, TTB, RC2I ) * Predict the Earth rotation angle for this UT1. ERA = iau_ERA00 ( UTA, UTB ) * Estimate s'. SP = iau_SP00 ( TTA, TTB ) * Form the polar motion matrix. CALL iau_POM00 ( XP, YP, SP, RPOM ) * Combine to form the celestial-to-terrestrial matrix. CALL iau_C2TCIO ( RC2I, ERA, RPOM, RC2T ) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2008 * Standards Of Fundamental Astronomy Review Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS * WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Review Board ("the Board"). * * 2. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the Software under the terms and * conditions specified herein does not imply that future versions * will also be made available under the same terms and conditions. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "as is" and the Board makes * no warranty as to its use or performance. The Board does not and * cannot warrant the performance or results which the user may * obtain by using the Software. The Board makes no warranties, * express or implied, as to non-infringement of third party rights, * merchantability, or fitness for any particular purpose. In no * event will the Board be liable to the user for any consequential, * incidental, or special damages, including any lost profits or lost * savings, even if a Board representative has been advised of such * damages, or for any claim by any third party. * * Correspondence concerning SOFA software should be addressed as * follows: * * Internet email: sofa@rl.ac.uk * Postal address: IAU SOFA Center * Rutherford Appleton Laboratory * Chilton, Didcot, Oxon OX11 0QX * United Kingdom * * *----------------------------------------------------------------------- END