SUBROUTINE iau_ATOI13 ( TYPE, OB1, OB2, UTC1, UTC2, DUT1, : ELONG, PHI, HM, XP, YP, PHPA, TC, RH, WL, : RI, DI, J ) *+ * - - - - - - - - - - - * i a u _ A T O I 1 3 * - - - - - - - - - - - * * Observed place to CIRS. 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: * TYPE c*(*) type of coordinates - 'R', 'H' or 'A' (Notes 1,2) * OB1 d observed Az, HA or RA (radians; Az is N=0,E=90) * OB2 d observed ZD or Dec (radians) * UTC1 d UTC as a 2-part... * UTC2 d ...quasi Julian Date (Notes 3,4) * DUT1 d UT1-UTC (seconds, Note 5) * ELONG d longitude (radians, east +ve, Note 6) * PHI d geodetic latitude (radians, Note 6) * HM d height above the ellipsoid (meters, Notes 6,8) * XP,YP d polar motion coordinates (radians, Note 7) * PHPA d pressure at the observer (hPa = mB, Note 8) * TC d ambient temperature at the observer (deg C) * RH d relative humidity at the observer (range 0-1) * WL d wavelength (micrometers, Note 9) * * Returned: * RI d CIRS right ascension (CIO-based, radians) * DI d CIRS declination (radians) * J i status: +1 = dubious year (Note 2) * 0 = OK * -1 = unacceptable date * * Notes: * * 1) "Observed" Az,ZD means the position that would be seen by a * perfect geodetically aligned theodolite. (Zenith distance is * used rather than altitude in order to reflect the fact that no * allowance is made for depression of the horizon.) This is * related to the observed HA,Dec via the standard rotation, using * the geodetic latitude (corrected for polar motion), while the * observed HA and (CIO-based) RA are related simply through the * Earth rotation angle and the site longitude. "Observed" RA,Dec * or HA,Dec thus means the position that would be seen by a perfect * equatorial with its polar axis aligned to the Earth's axis of * rotation. * * 2) Only the first character of the TYPE argument is significant. * 'R' or 'r' indicates that OB1 and OB2 are the observed right * ascension and declination; 'H' or 'h' indicates that they are * hour angle (west +ve) and declination; anything else ('A' or * 'a' is recommended) indicates that OB1 and OB2 are azimuth * (north zero, east 90 deg) and zenith distance. * * 3) 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. * * 4) 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. * * 5) 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. * * 6) 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. * * 7) 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. * * 8) 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. * * 9) 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). * * 10) The accuracy of the result is limited by the corrections for * refraction, which use a simple A*tan(z) + B*tan^3(z) model. * Providing the meteorological parameters are known accurately and * there are no gross local effects, the predicted astrometric * coordinates should be within 0.05 arcsec (optical) or 1 arcsec * (radio) for a zenith distance of less than 70 degrees, better * than 30 arcsec (optical or radio) at 85 degrees and better * than 20 arcmin (optical) or 30 arcmin (radio) at the horizon. * * Without refraction, the complementary routines iau_ATIO13 and * iau_ATOI13 are self-consistent to better than 1 microarcsecond * all over the celestial sphere. With refraction included, * consistency falls off at high zenith distances, but is still * better than 0.05 arcsec at 85 degrees. * * 11) 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. * * Called: * iau_APIO13 astrometry parameters, CIRS-observed, 2013 * iau_ATOIQ quick observed to CIRS * * This revision: 2022 August 30 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE CHARACTER*(*) TYPE DOUBLE PRECISION OB1, OB2, UTC1, UTC2, DUT1, ELONG, PHI, HM, : XP, YP, PHPA, TC, RH, WL, RI, DI INTEGER J INTEGER JS DOUBLE PRECISION ASTROM(30) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Star-independent astrometry parameters for CIRS->observed. CALL iau_APIO13 ( UTC1, UTC2, DUT1, ELONG, PHI, HM, XP, YP, : PHPA, TC, RH, WL, ASTROM, JS ) * Abort if bad UTC. IF ( JS.LT.0 ) GO TO 9 * Transform observed to CIRS. CALL iau_ATOIQ ( TYPE, OB1, OB2, ASTROM, RI, DI ) * Return OK/warning 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. 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