SUBROUTINE iau_TAIUTC ( TAI1, TAI2, UTC1, UTC2, J ) *+ * - - - - - - - - - - - * i a u _ T A I U T C * - - - - - - - - - - - * * Time scale transformation: International Atomic Time, TAI, to * Coordinated Universal Time, UTC. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: canonical. * * Given: * TAI1,TAI2 d TAI as a 2-part Julian Date (Note 1) * * Returned: * UTC1,UTC2 d UTC as a 2-part quasi Julian Date (Notes 1-3) * J i status: +1 = dubious year (Note 4) * 0 = OK * -1 = unacceptable date * * Notes: * * 1) TAI1+TAI2 is Julian Date, apportioned in any convenient way * between the two arguments, for example where TAI1 is the Julian * Day Number and TAI2 is the fraction of a day. The returned UTC1 * and UTC2 form an analogous pair, except that a special convention * is used, to deal with the problem of leap seconds - see the next * note. * * 2) 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. In the 1960-1972 era there were * smaller jumps (in either direction) each time the linear UTC(TAI) * expression was changed, and these "mini-leaps" are also included * in the SOFA convention. * * 3) The routine iau_D2DTF can be used to transform the UTC quasi-JD * into calendar date and clock time, including UTC leap second * handling. * * 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. * * Called: * iau_UTCTAI UTC to TAI * * References: * * McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), * IERS Technical Note No. 32, BKG (2004) * * Explanatory Supplement to the Astronomical Almanac, * P. Kenneth Seidelmann (ed), University Science Books (1992) * * This revision: 2020 June 22 * * SOFA release 2021-05-12 * * Copyright (C) 2021 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION TAI1, TAI2, UTC1, UTC2 INTEGER J LOGICAL BIG1 INTEGER I, JS DOUBLE PRECISION A1, A2, U1, U2, G1, G2 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Put the two parts of the TAI into big-first order. BIG1 = ABS(TAI1) .GE. ABS(TAI2) IF ( BIG1 ) THEN A1 = TAI1 A2 = TAI2 ELSE A1 = TAI2 A2 = TAI1 END IF * Initial guess for UTC. U1 = A1 U2 = A2 * Iterate (though in most cases just once is enough). DO 1 I=1,3 * Guessed UTC to TAI. CALL iau_UTCTAI ( U1, U2, G1, G2, JS ) IF ( JS.LT.0 ) GO TO 9 * Adjust guessed UTC. U2 = U2 + (A1-G1) U2 = U2 + (A2-G2) 1 CONTINUE * Return the UTC result, preserving the TAI order. IF ( BIG1 ) THEN UTC1 = U1 UTC2 = U2 ELSE UTC1 = U2 UTC2 = U1 END IF * Status. 9 CONTINUE J = JS * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2021 * 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