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#include "erfa.h"
void eraPr00(double date1, double date2, double *dpsipr, double *depspr)
/*
** - - - - - - - -
** e r a P r 0 0
** - - - - - - - -
**
** Precession-rate part of the IAU 2000 precession-nutation models
** (part of MHB2000).
**
** Given:
** date1,date2 double TT as a 2-part Julian Date (Note 1)
**
** Returned:
** dpsipr,depspr double precession corrections (Notes 2,3)
**
** 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 precession adjustments are expressed as "nutation
** components", corrections in longitude and obliquity with respect
** to the J2000.0 equinox and ecliptic.
**
** 3) Although the precession adjustments are stated to be with respect
** to Lieske et al. (1977), the MHB2000 model does not specify which
** set of Euler angles are to be used and how the adjustments are to
** be applied. The most literal and straightforward procedure is to
** adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
** to add dpsipr to psi_A and depspr to both omega_A and eps_A.
**
** 4) This is an implementation of one aspect of the IAU 2000A nutation
** model, formally adopted by the IAU General Assembly in 2000,
** namely MHB2000 (Mathews et al. 2002).
**
** References:
**
** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
** for the precession quantities based upon the IAU (1976) System of
** Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
**
** Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
** and precession New nutation series for nonrigid Earth and
** insights into the Earth's interior", J.Geophys.Res., 107, B4,
** 2002. The MHB2000 code itself was obtained on 9th September 2002
** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
**
** Wallace, P.T., "Software for Implementing the IAU 2000
** Resolutions", in IERS Workshop 5.1 (2002).
**
** Copyright (C) 2013-2016, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
double t;
/* Precession and obliquity corrections (radians per century) */
static const double PRECOR = -0.29965 * ERFA_DAS2R,
OBLCOR = -0.02524 * ERFA_DAS2R;
/* Interval between fundamental epoch J2000.0 and given date (JC). */
t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
/* Precession rate contributions with respect to IAU 1976/80. */
*dpsipr = PRECOR * t;
*depspr = OBLCOR * t;
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.
**
*/
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