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. * * 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 and that are too far in the future * to be trusted. See iau_DAT for further details. * * Called: * iau_JD2CAL JD to Gregorian calendar * iau_DAT delta(AT) = TAI-UTC * iau_CAL2JD Gregorian calendar to JD * * 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: 2010 May 14 * * SOFA release 2012-03-01 * * Copyright (C) 2012 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION TAI1, TAI2, UTC1, UTC2 INTEGER J * Days to seconds DOUBLE PRECISION D2S PARAMETER ( D2S = 86400D0 ) LOGICAL BIG1 INTEGER I, IY, IM, ID, JS, JW DOUBLE PRECISION A1, A2, D1, DATS1, D2, FD, DDATS, DATS2, DATD, : AS1, AS2, DA * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Put the two parts of the TAI into big-first order. BIG1 = TAI1.GE.TAI2 IF ( BIG1 ) THEN A1 = TAI1 A2 = TAI2 ELSE A1 = TAI2 A2 = TAI1 END IF * See if the TAI can possibly be in a leap-second day. D1 = A1 DATS1 = 0D0 DO 1 I=-1,3 D2 = A2 + DBLE(I) CALL iau_JD2CAL ( D1, D2, IY, IM, ID, FD, JS ) IF ( JS.NE.0 ) GO TO 9 CALL iau_DAT ( IY, IM, ID, 0D0, DATS2, JS ) IF ( JS.LT.0 ) GO TO 9 IF ( I.EQ.-1 ) DATS1 = DATS2 DDATS = DATS2 - DATS1 DATD = DATS1 / D2S IF ( ABS(DDATS).GE.0.5D0 ) THEN * Yes. Get TAI for the start of the UTC day that ends in a leap. CALL iau_CAL2JD ( IY, IM, ID, D1, D2, JW ) IF ( JW.NE.0 ) THEN JS = JW GO TO 9 END IF AS1 = D1 AS2 = D2 - 1D0 + DATD * Is the TAI after this point? DA = A1 - AS1 DA = DA + ( A2 - AS2 ) IF ( DA.GT.0D0 ) THEN * Yes: fraction of the current UTC day that has elapsed. FD = DA * D2S / ( D2S + DDATS ) * Ramp TAI-UTC to bring about SOFA's JD(UTC) convention. DATD = DATD + DDATS*MIN(FD,1D0)/D2S END IF * Break. GO TO 2 END IF DATS1 = DATS2 1 CONTINUE 2 CONTINUE * Subtract the (possibly adjusted) TAI-UTC from TAI to give UTC. A2 = A2 - DATD * Return the UTC result, preserving the TAI order. IF ( BIG1 ) THEN UTC1 = A1 UTC2 = A2 ELSE UTC1 = A2 UTC2 = A1 END IF * Status. 9 CONTINUE IF ( JS.LT.0 ) JS = -1 J = JS * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2012 * 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. All * variations, no matter how minor, must be explicitly marked as * such, as explained above. * * 4. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or * by inappropriate modification. * * 5. The SOFA software is provided "as is" and SOFA makes no warranty * as to its use or performance. SOFA does not and cannot warrant * the performance or results which the user may obtain by using the * SOFA software. SOFA makes no warranties, express or implied, as * to non-infringement of third party rights, merchantability, or * fitness for any particular purpose. In no event will SOFA be * liable to the user for any consequential, incidental, or special * damages, including any lost profits or lost savings, even if a * SOFA representative has been advised of such damages, or for any * claim by any third party. * * 6. 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