SUBROUTINE iau_APER13 ( UT11, UT12, ASTROM ) *+ * - - - - - - - - - - - * i a u _ A P E R 1 3 * - - - - - - - - - - - * * In the star-independent astrometry parameters, update only the * Earth rotation angle. The caller provides UT1 (n.b. not UTC). * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * UT11 d UT1 as a 2-part... * UT12 d ...Julian Date (Note 1) * ASTROM d(30) star-independent astrometry parameters: * (1) not used * (2-4) not used * (5-7) not used * (8) not used * (9-11) not used * (12) not used * (13-21) not used * (22) longitude + s' (radians) * (23) not used * (24) not used * (25) not used * (26) not used * (27) not used * (28) not used * (29) not used * (30) not used * * Returned: * ASTROM d(30) star-independent astrometry parameters: * (1) unchanged * (2-4) unchanged * (5-7) unchanged * (8) unchanged * (9-11) unchanged * (12) unchanged * (13-21) unchanged * (22) unchanged * (23) unchanged * (24) unchanged * (25) unchanged * (26) unchanged * (27) unchanged * (28) "local" Earth rotation angle (radians) * (29) unchanged * (30) unchanged * * Notes: * * 1) The UT1 date (n.b. not UTC) UT11+UT12 is a Julian Date, * apportioned in any convenient way between the arguments UT11 and * UT12. For example, JD(UT1)=2450123.7 could be expressed in any * of these ways, among others: * * UT11 UT12 * * 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. The date & time method is * best matched to the algorithm used: maximum precision is * delivered when the UT11 argument is for 0hrs UT1 on the day in * question and the UT12 argument lies in the range 0 to 1, or vice * versa. * * 2) If the caller wishes to provide the Earth rotation angle itself, * the routine iau_APER can be used instead. One use of this * technique is to substitute Greenwich apparent sidereal time and * thereby to support equinox based transformations directly. * * 3) This is one of several routines that inserts into the ASTROM * array star-independent parameters needed for the chain of * astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed. * * The various routines support different classes of observer and * portions of the transformation chain: * * routines observer transformation * * iau_APCG iau_APCG13 geocentric ICRS <-> GCRS * iau_APCI iau_APCI13 terrestrial ICRS <-> CIRS * iau_APCO iau_APCO13 terrestrial ICRS <-> observed * iau_APCS iau_APCS13 space ICRS <-> GCRS * iau_APER iau_APER13 terrestrial update Earth rotation * iau_APIO iau_APIO13 terrestrial CIRS <-> observed * * Those with names ending in "13" use contemporary SOFA models to * compute the various ephemerides. The others accept ephemerides * supplied by the caller. * * The transformation from ICRS to GCRS covers space motion, * parallax, light deflection, and aberration. From GCRS to CIRS * comprises frame bias and precession-nutation. From CIRS to * observed takes account of Earth rotation, polar motion, diurnal * aberration and parallax (unless subsumed into the ICRS <-> GCRS * transformation), and atmospheric refraction. * * Called: * iau_APER astrometry parameters: update ERA * iau_ERA00 Earth rotation angle, IAU 2000 * * This revision: 2017 March 12 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION UT11, UT12, ASTROM(30) DOUBLE PRECISION iau_ERA00 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - CALL iau_APER ( iau_ERA00 ( UT11, UT12 ), ASTROM ) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2023 * Standards of Fundamental Astronomy Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND * CONDITIONS WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Board ("SOFA"). * * 2. Permission is granted to anyone to use the SOFA software for any * purpose, including commercial applications, free of charge and * without payment of royalties, subject to the conditions and * restrictions listed below. * * 3. You (the user) may copy and distribute SOFA source code to others, * and use and adapt its code and algorithms in your own software, * on a world-wide, royalty-free basis. 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