#include "sofa.h" double iauEe00b(double date1, double date2) /* ** - - - - - - - - - ** i a u E e 0 0 b ** - - - - - - - - - ** ** Equation of the equinoxes, compatible with IAU 2000 resolutions but ** using the truncated nutation model IAU 2000B. ** ** This function is part of the International Astronomical Union's ** SOFA (Standards Of Fundamental Astronomy) software collection. ** ** Status: support function. ** ** Given: ** date1,date2 double TT as a 2-part Julian Date (Note 1) ** ** Returned (function value): ** double equation of the equinoxes (Note 2) ** ** Notes: ** ** 1) The TT date date1+date2 is a Julian Date, apportioned in any ** convenient way between the two arguments. For example, ** JD(TT)=2450123.7 could be expressed in any of these ways, ** among others: ** ** date1 date2 ** ** 2450123.7 0.0 (JD method) ** 2451545.0 -1421.3 (J2000 method) ** 2400000.5 50123.2 (MJD method) ** 2450123.5 0.2 (date & time method) ** ** The JD method is the most natural and convenient to use in ** cases where the loss of several decimal digits of resolution ** is acceptable. The J2000 method is best matched to the way ** the argument is handled internally and will deliver the ** optimum resolution. The MJD method and the date & time methods ** are both good compromises between resolution and convenience. ** ** 2) The result, which is in radians, operates in the following sense: ** ** Greenwich apparent ST = GMST + equation of the equinoxes ** ** 3) The result is compatible with the IAU 2000 resolutions except ** that accuracy has been compromised for the sake of speed. For ** further details, see McCarthy & Luzum (2001), IERS Conventions ** 2003 and Capitaine et al. (2003). ** ** Called: ** iauPr00 IAU 2000 precession adjustments ** iauObl80 mean obliquity, IAU 1980 ** iauNut00b nutation, IAU 2000B ** iauEe00 equation of the equinoxes, IAU 2000 ** ** References: ** ** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to ** implement the IAU 2000 definition of UT1", Astronomy & ** Astrophysics, 406, 1135-1149 (2003) ** ** McCarthy, D.D. & Luzum, B.J., "An abridged model of the ** precession-nutation of the celestial pole", Celestial Mechanics & ** Dynamical Astronomy, 85, 37-49 (2003) ** ** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), ** IERS Technical Note No. 32, BKG (2004) ** ** This revision: 2008 May 18 ** ** Copyright (C) 2008 IAU SOFA Review Board. See notes at end. */ { double dpsipr, depspr, epsa, dpsi, deps, ee; /* IAU 2000 precession-rate adjustments. */ iauPr00(date1, date2, &dpsipr, &depspr); /* Mean obliquity, consistent with IAU 2000 precession-nutation. */ epsa = iauObl80(date1, date2) + depspr; /* Nutation in longitude. */ iauNut00b(date1, date2, &dpsi, &deps); /* Equation of the equinoxes. */ ee = iauEe00(date1, date2, epsa, dpsi); return ee; /*----------------------------------------------------------------------- ** ** Copyright (C) 2008 ** Standards Of Fundamental Astronomy Review Board ** of the International Astronomical Union. ** ** ===================== ** SOFA Software License ** ===================== ** ** NOTICE TO USER: ** ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS ** WHICH APPLY TO ITS USE. ** ** 1. The Software is owned by the IAU SOFA Review Board ("the Board"). ** ** 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 adapt the SOFA software and its ** algorithms for your own purposes and you may copy and distribute ** a resulting "derived work" to others on a world-wide, royalty-free ** basis, provided that the derived work complies 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 contain ** software provided by SOFA or software that has been distributed ** by or endorsed by SOFA. ** ** b) The source code of your derived work must contain descriptions ** of how the derived work is based upon and/or differs from the ** original SOFA software. ** ** c) The name(s) of all routine(s) that you distribute shall differ ** from the SOFA names, even when the SOFA content has not been ** otherwise changed. ** ** d) The routine-naming prefix "iau" shall not be used. ** ** e) 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. ** ** f) 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. ** ** 4. In any published work or commercial products which includes ** results achieved by using the SOFA software, you shall acknowledge ** that the SOFA software was used in obtaining those results. ** ** 5. You shall not cause the SOFA software to be brought into ** disrepute, either by misuse, or use for inappropriate tasks, or by ** inappropriate modification. ** ** 6. The SOFA software is provided "as is" and the Board makes no ** warranty as to its use or performance. The Board does not and ** cannot warrant the performance or results which the user may obtain ** by using the SOFA software. The Board 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 the Board be liable to the user for any consequential, ** incidental, or special damages, including any lost profits or lost ** savings, even if a Board representative has been advised of such ** damages, or for any claim by any third party. ** ** 7. 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. ** ** Correspondence concerning SOFA software should be addressed as ** follows: ** ** Internet email: sofa@rl.ac.uk ** Postal address: IAU SOFA Center ** Rutherford Appleton Laboratory ** Chilton, Didcot, Oxon OX11 0QX ** United Kingdom ** **---------------------------------------------------------------------*/ }