#include "sofam.h" int iauStarpm(double ra1, double dec1, double pmr1, double pmd1, double px1, double rv1, double ep1a, double ep1b, double ep2a, double ep2b, double *ra2, double *dec2, double *pmr2, double *pmd2, double *px2, double *rv2) /* ** - - - - - - - - - - ** i a u S t a r p m ** - - - - - - - - - - ** ** Star proper motion: update star catalog data for space motion. ** ** This function is part of the International Astronomical Union's ** SOFA (Standards Of Fundamental Astronomy) software collection. ** ** Status: support function. ** ** Given: ** ra1 double right ascension (radians), before ** dec1 double declination (radians), before ** pmr1 double RA proper motion (radians/year), before ** pmd1 double Dec proper motion (radians/year), before ** px1 double parallax (arcseconds), before ** rv1 double radial velocity (km/s, +ve = receding), before ** ep1a double "before" epoch, part A (Note 1) ** ep1b double "before" epoch, part B (Note 1) ** ep2a double "after" epoch, part A (Note 1) ** ep2b double "after" epoch, part B (Note 1) ** ** Returned: ** ra2 double right ascension (radians), after ** dec2 double declination (radians), after ** pmr2 double RA proper motion (radians/year), after ** pmd2 double Dec proper motion (radians/year), after ** px2 double parallax (arcseconds), after ** rv2 double radial velocity (km/s, +ve = receding), after ** ** Returned (function value): ** int status: ** -1 = system error (should not occur) ** 0 = no warnings or errors ** 1 = distance overridden (Note 6) ** 2 = excessive velocity (Note 7) ** 4 = solution didn't converge (Note 8) ** else = binary logical OR of the above warnings ** ** Notes: ** ** 1) The starting and ending TDB dates ep1a+ep1b and ep2a+ep2b are ** Julian Dates, apportioned in any convenient way between the two ** parts (A and B). For example, JD(TDB)=2450123.7 could be ** expressed in any of these ways, among others: ** ** epna epnb ** ** 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) In accordance with normal star-catalog conventions, the object's ** right ascension and declination are freed from the effects of ** secular aberration. The frame, which is aligned to the catalog ** equator and equinox, is Lorentzian and centered on the SSB. ** ** The proper motions are the rate of change of the right ascension ** and declination at the catalog epoch and are in radians per TDB ** Julian year. ** ** The parallax and radial velocity are in the same frame. ** ** 3) Care is needed with units. The star coordinates are in radians ** and the proper motions in radians per Julian year, but the ** parallax is in arcseconds. ** ** 4) The RA proper motion is in terms of coordinate angle, not true ** angle. If the catalog uses arcseconds for both RA and Dec proper ** motions, the RA proper motion will need to be divided by cos(Dec) ** before use. ** ** 5) Straight-line motion at constant speed, in the inertial frame, ** is assumed. ** ** 6) An extremely small (or zero or negative) parallax is interpreted ** to mean that the object is on the "celestial sphere", the radius ** of which is an arbitrary (large) value (see the iauStarpv ** function for the value used). When the distance is overridden in ** this way, the status, initially zero, has 1 added to it. ** ** 7) If the space velocity is a significant fraction of c (see the ** constant VMAX in the function iauStarpv), it is arbitrarily set ** to zero. When this action occurs, 2 is added to the status. ** ** 8) The relativistic adjustment carried out in the iauStarpv function ** involves an iterative calculation. If the process fails to ** converge within a set number of iterations, 4 is added to the ** status. ** ** Called: ** iauStarpv star catalog data to space motion pv-vector ** iauPvu update a pv-vector ** iauPdp scalar product of two p-vectors ** iauPvstar space motion pv-vector to star catalog data ** ** This revision: 2008 May 16 ** ** SOFA release 2012-03-01 ** ** Copyright (C) 2012 IAU SOFA Board. See notes at end. */ { double pv1[2][3], tl1, dt, pv[2][3], r2, rdv, v2, c2mv2, tl2, pv2[2][3]; int j1, j2, j; /* RA,Dec etc. at the "before" epoch to space motion pv-vector. */ j1 = iauStarpv(ra1, dec1, pmr1, pmd1, px1, rv1, pv1); /* Light time when observed (days). */ tl1 = iauPm(pv1[0]) / DC; /* Time interval, "before" to "after" (days). */ dt = (ep2a - ep1a) + (ep2b - ep1b); /* Move star along track from the "before" observed position to the */ /* "after" geometric position. */ iauPvu(dt + tl1, pv1, pv); /* From this geometric position, deduce the observed light time (days) */ /* at the "after" epoch (with theoretically unneccessary error check). */ r2 = iauPdp(pv[0], pv[0]); rdv = iauPdp(pv[0], pv[1]); v2 = iauPdp(pv[1], pv[1]); c2mv2 = DC*DC - v2; if (c2mv2 <= 0) return -1; tl2 = (-rdv + sqrt(rdv*rdv + c2mv2*r2)) / c2mv2; /* Move the position along track from the observed place at the */ /* "before" epoch to the observed place at the "after" epoch. */ iauPvu(dt + (tl1 - tl2), pv1, pv2); /* Space motion pv-vector to RA,Dec etc. at the "after" epoch. */ j2 = iauPvstar(pv2, ra2, dec2, pmr2, pmd2, px2, rv2); /* Final status. */ j = (j2 == 0) ? j1 : -1; return j; /*---------------------------------------------------------------------- ** ** 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 ** **--------------------------------------------------------------------*/ }