SUBROUTINE iau_APER ( THETA, ASTROM ) *+ * - - - - - - - - - * i a u _ A P E R * - - - - - - - - - * * In the star-independent astrometry parameters, update only the * Earth rotation angle, supplied by the caller explicitly. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * THETA d Earth rotation angle (radians, Note 2) * 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) This routine exists to enable sidereal-tracking applications to * avoid wasteful recomputation of the bulk of the astrometry * parameters: only the Earth rotation is updated. * * 2) For targets expressed as equinox based positions, such as * classical geocentric apparent (RA,Dec), the supplied THETA can be * Greenwich apparent sidereal time rather than Earth rotation * angle. * * 3) The routine iau_APER13 can be used instead of the present routine, * and starts from UT1 rather than ERA itself. * * 4) 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. * * This revision: 2013 September 25 * * SOFA release 2018-01-30 * * Copyright (C) 2018 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION THETA, ASTROM(30) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ASTROM(28) = THETA + ASTROM(22) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2018 * 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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The provision of any version of the SOFA 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. * * In any published work or commercial product which uses the SOFA * software directly, acknowledgement (see www.iausofa.org) is * appreciated. * * Correspondence concerning SOFA software should be addressed as * follows: * * By email: sofa@ukho.gov.uk * By post: IAU SOFA Center * HM Nautical Almanac Office * UK Hydrographic Office * Admiralty Way, Taunton * Somerset, TA1 2DN * United Kingdom * *----------------------------------------------------------------------- END