diff options
Diffstat (limited to 'ast/erfa/pfw06.c')
| -rw-r--r-- | ast/erfa/pfw06.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/ast/erfa/pfw06.c b/ast/erfa/pfw06.c new file mode 100644 index 0000000..b510f0a --- /dev/null +++ b/ast/erfa/pfw06.c @@ -0,0 +1,174 @@ +#include "erfa.h" + +void eraPfw06(double date1, double date2, + double *gamb, double *phib, double *psib, double *epsa) +/* +** - - - - - - - - - +** e r a P f w 0 6 +** - - - - - - - - - +** +** Precession angles, IAU 2006 (Fukushima-Williams 4-angle formulation). +** +** Given: +** date1,date2 double TT as a 2-part Julian Date (Note 1) +** +** Returned: +** gamb double F-W angle gamma_bar (radians) +** phib double F-W angle phi_bar (radians) +** psib double F-W angle psi_bar (radians) +** epsa double F-W angle epsilon_A (radians) +** +** 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) Naming the following points: +** +** e = J2000.0 ecliptic pole, +** p = GCRS pole, +** E = mean ecliptic pole of date, +** and P = mean pole of date, +** +** the four Fukushima-Williams angles are as follows: +** +** gamb = gamma_bar = epE +** phib = phi_bar = pE +** psib = psi_bar = pEP +** epsa = epsilon_A = EP +** +** 3) The matrix representing the combined effects of frame bias and +** precession is: +** +** PxB = R_1(-epsa).R_3(-psib).R_1(phib).R_3(gamb) +** +** 4) The matrix representing the combined effects of frame bias, +** precession and nutation is simply: +** +** NxPxB = R_1(-epsa-dE).R_3(-psib-dP).R_1(phib).R_3(gamb) +** +** where dP and dE are the nutation components with respect to the +** ecliptic of date. +** +** Reference: +** +** Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351 +** +** Called: +** eraObl06 mean obliquity, IAU 2006 +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double t; + + +/* Interval between fundamental date J2000.0 and given date (JC). */ + t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC; + +/* P03 bias+precession angles. */ + *gamb = ( -0.052928 + + ( 10.556378 + + ( 0.4932044 + + ( -0.00031238 + + ( -0.000002788 + + ( 0.0000000260 ) + * t) * t) * t) * t) * t) * ERFA_DAS2R; + *phib = ( 84381.412819 + + ( -46.811016 + + ( 0.0511268 + + ( 0.00053289 + + ( -0.000000440 + + ( -0.0000000176 ) + * t) * t) * t) * t) * t) * ERFA_DAS2R; + *psib = ( -0.041775 + + ( 5038.481484 + + ( 1.5584175 + + ( -0.00018522 + + ( -0.000026452 + + ( -0.0000000148 ) + * t) * t) * t) * t) * t) * ERFA_DAS2R; + *epsa = eraObl06(date1, date2); + + return; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** All rights reserved. +** +** This library is derived, with permission, from the International +** Astronomical Union's "Standards of Fundamental Astronomy" library, +** available from http://www.iausofa.org. +** +** The ERFA version is intended to retain identical functionality to +** the SOFA library, but made distinct through different function and +** file names, as set out in the SOFA license conditions. The SOFA +** original has a role as a reference standard for the IAU and IERS, +** and consequently redistribution is permitted only in its unaltered +** state. The ERFA version is not subject to this restriction and +** therefore can be included in distributions which do not support the +** concept of "read only" software. +** +** Although the intent is to replicate the SOFA API (other than +** replacement of prefix names) and results (with the exception of +** bugs; any that are discovered will be fixed), SOFA is not +** responsible for any errors found in this version of the library. +** +** If you wish to acknowledge the SOFA heritage, please acknowledge +** that you are using a library derived from SOFA, rather than SOFA +** itself. +** +** +** TERMS AND CONDITIONS +** +** Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions +** are met: +** +** 1 Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** +** 2 Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** +** 3 Neither the name of the Standards Of Fundamental Astronomy Board, +** the International Astronomical Union nor the names of its +** contributors may be used to endorse or promote products derived +** from this software without specific prior written permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +** POSSIBILITY OF SUCH DAMAGE. +** +*/ |