SUBROUTINE iau_APIO13 ( UTC1, UTC2, DUT1, ELONG, PHI, HM, XP, YP, : PHPA, TC, RH, WL, ASTROM, J ) *+ * - - - - - - - - - - - * i a u _ A P I O 1 3 * - - - - - - - - - - - * * For a terrestrial observer, prepare star-independent astrometry * parameters for transformations between CIRS and observed coordinates. * The caller supplies UTC, site coordinates, ambient air conditions and * observing wavelength. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * UTC1 d UTC as a 2-part... * UTC2 d ...quasi Julian Date (Notes 1,2) * DUT1 d UT1-UTC (seconds) * ELONG d longitude (radians, east +ve, Note 3) * PHI d geodetic latitude (radians, Note 3) * HM d height above ellipsoid (m, geodetic Notes 4,6) * XP,YP d polar motion x-coordinates (radians, Note 5) * PHPA d pressure at the observer (hPa = mB, Note 6) * TC d ambient temperature at the observer (deg C) * RH d relative humidity at the observer (range 0-1) * WL d wavelength (micrometers, Note 7) * * 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) longitude + s' (radians) * (23) polar motion xp wrt local meridian (radians) * (24) polar motion yp wrt local meridian (radians) * (25) sine of geodetic latitude * (26) cosine of geodetic latitude * (27) magnitude of diurnal aberration vector * (28) "local" Earth rotation angle (radians) * (29) refraction constant A (radians) * (30) refraction constant B (radians) * J i status: +1 = dubious year (Note 2) * 0 = OK * -1 = unacceptable date * * Notes: * * 1) UTC1+UTC2 is quasi Julian Date (see Note 2), apportioned in any * convenient way between the two arguments, for example where UTC1 * is the Julian Day Number and UTC2 is the fraction of a day. * * However, JD cannot unambiguously represent UTC during a leap * second unless special measures are taken. The convention in the * present routine is that the JD day represents UTC days whether * the length is 86399, 86400 or 86401 SI seconds. * * Applications should use the routine iau_DTF2D to convert from * calendar date and time of day into 2-part quasi Julian Date, as * it implements the leap-second-ambiguity convention just * described. * * 2) The warning status "dubious year" flags UTCs that predate the * introduction of the time scale or that are too far in the future * to be trusted. See iau_DAT for further details. * * 3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly * one second at the end of each positive UTC leap second, * introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This * practice is under review, and in the future UT1-UTC may grow * essentially without limit. * * 4) The geographical coordinates are with respect to the WGS84 * reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the * longitude required by the present routine is east-positive * (i.e. right-handed), in accordance with geographical convention. * * 5) The polar motion XP,YP can be obtained from IERS bulletins. The * values 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 0 and 90 deg west respectively. For many applications, * XP and YP can be set to zero. * * Internally, the polar motion is stored in a form rotated onto * the local meridian. * * 6) If hm, the height above the ellipsoid of the observing station * in meters, is not known but phpa, the pressure in hPa (=mB), is * available, an adequate estimate of hm can be obtained from the * expression * * hm = -29.3 * tsl * log ( phpa / 1013.25 ); * * where tsl is the approximate sea-level air temperature in K * (See Astrophysical Quantities, C.W.Allen, 3rd edition, section * 52). Similarly, if the pressure phpa is not known, it can be * estimated from the height of the observing station, hm, as * follows: * * phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) ); * * Note, however, that the refraction is nearly proportional to the * pressure and that an accurate phpa value is important for * precise work. * * 7) The argument WL specifies the observing wavelength in * micrometers. The transition from optical to radio is assumed to * occur at 100 micrometers (about 3000 GHz). * * 8) It is advisable to take great care with units, as even unlikely * values of the input parameters are accepted and processed in * accordance with the models used. * * 9) In cases where the caller wishes to supply his own Earth * rotation information and refraction constants, the routine * iau_APC can be used instead of the present routine. * * 10) 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. * * 11) The context array ASTROM produced by this routine is used by * iau_ATIOQ and iau_ATOIQ. * * Called: * iau_UTCTAI UTC to TAI * iau_TAITT TAI to TT * iau_UTCUT1 UTC to UT1 * iau_SP00 the TIO locator s', IERS 2000 * iau_ERA00 Earth rotation angle, IAU 2000 * iau_REFCO refraction constants for given ambient conditions * iau_APIO astrometry parameters, CIRS-observed * * This revision: 2013 September 25 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION UTC1, UTC2, DUT1, ELONG, PHI, HM, XP, YP, : PHPA, TC, RH, WL, ASTROM(30) INTEGER J INTEGER JS DOUBLE PRECISION TAI1, TAI2, TT1, TT2, UT11, UT12, SP, THETA, : REFA, REFB DOUBLE PRECISION iau_SP00, iau_ERA00 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * UTC to other time scales. CALL iau_UTCTAI ( UTC1, UTC2, TAI1, TAI2, JS ) CALL iau_TAITT ( TAI1, TAI2, TT1, TT2, JS ) CALL iau_UTCUT1 ( UTC1, UTC2, DUT1, UT11, UT12, JS ) * Abort if error. IF ( JS.LT.0 ) GO TO 9 * TIO locator s'. SP = iau_SP00 ( TT1, TT2 ) * Earth rotation angle. THETA = iau_ERA00 ( UT11, UT12 ) * Refraction constants A and B. CALL iau_REFCO ( PHPA, TC, RH, WL, REFA, REFB ) * CIRS <-> observed astrometry parameters. CALL iau_APIO ( SP, THETA, ELONG, PHI, HM, XP, YP, REFA, REFB, : ASTROM ) * Return the status. 9 CONTINUE J = JS * 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. That portion of your * distribution that does not consist of intact and unchanged copies * of SOFA source code files is a "derived work" that must comply * with the following requirements: * * a) Your work shall be marked or carry a statement that it * (i) uses routines and computations derived by you from * software provided by SOFA under license to you; and * (ii) does not itself constitute software provided by and/or * endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon, contains and/or differs * from the original SOFA software. * * c) The names of all routines in your derived work shall not * include the prefix "iau" or "sofa" or trivial modifications * thereof such as changes of case. * * d) The origin of the SOFA components of your derived work must * not be misrepresented; you must not claim that you wrote the * original software, nor file a patent application for SOFA * software or algorithms embedded in the SOFA software. * * e) These requirements must be reproduced intact in any source * distribution and shall apply to anyone to whom you have * granted a further right to modify the source code of your * derived work. * * Note that, as originally distributed, the SOFA software is * intended to be a definitive implementation of the IAU standards, * and consequently third-party modifications are discouraged. 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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