#include "erfa.h"
void eraPmpx(double rc, double dc, double pr, double pd,
double px, double rv, double pmt, double pob[3],
double pco[3])
/*
** - - - - - - - -
** e r a P m p x
** - - - - - - - -
**
** Proper motion and parallax.
**
** Given:
** rc,dc double ICRS RA,Dec at catalog epoch (radians)
** pr double RA proper motion (radians/year; Note 1)
** pd double Dec proper motion (radians/year)
** px double parallax (arcsec)
** rv double radial velocity (km/s, +ve if receding)
** pmt double proper motion time interval (SSB, Julian years)
** pob double[3] SSB to observer vector (au)
**
** Returned:
** pco double[3] coordinate direction (BCRS unit vector)
**
** Notes:
**
** 1) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
**
** 2) The proper motion time interval is for when the starlight
** reaches the solar system barycenter.
**
** 3) To avoid the need for iteration, the Roemer effect (i.e. the
** small annual modulation of the proper motion coming from the
** changing light time) is applied approximately, using the
** direction of the star at the catalog epoch.
**
** References:
**
** 1984 Astronomical Almanac, pp B39-B41.
**
** Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
** the Astronomical Almanac, 3rd ed., University Science Books
** (2013), Section 7.2.
**
** Called:
** eraPdp scalar product of two p-vectors
** eraPn decompose p-vector into modulus and direction
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
/* Km/s to au/year */
const double VF = ERFA_DAYSEC*ERFA_DJM/ERFA_DAU;
/* Light time for 1 au, Julian years */
const double AULTY = ERFA_AULT/ERFA_DAYSEC/ERFA_DJY;
int i;
double sr, cr, sd, cd, x, y, z, p[3], dt, pxr, w, pdz, pm[3];
/* Spherical coordinates to unit vector (and useful functions). */
sr = sin(rc);
cr = cos(rc);
sd = sin(dc);
cd = cos(dc);
p[0] = x = cr*cd;
p[1] = y = sr*cd;
p[2] = z = sd;
/* Proper motion time interval (y) including Roemer effect. */
dt = pmt + eraPdp(p,pob)*AULTY;
/* Space motion (radians per year). */
pxr = px * ERFA_DAS2R;
w = VF * rv * pxr;
pdz = pd * z;
pm[0] = - pr*y - pdz*cr + w*x;
pm[1] = pr*x - pdz*sr + w*y;
pm[2] = pd*cd + w*z;
/* Coordinate direction of star (unit vector, BCRS). */
for (i = 0; i < 3; i++) {
p[i] += dt*pm[i] - pxr*pob[i];
}
eraPn(p, &w, pco);
/* Finished. */
}
/*----------------------------------------------------------------------
**
**
** Copyright (C) 2013-2014, 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.
**
*/