SUBROUTINE iau_PVSTAR ( PV, RA, DEC, PMR, PMD, PX, RV, J ) *+ * - - - - - - - - - - - * i a u _ P V S T A R * - - - - - - - - - - - * * Convert star position+velocity vector to catalog coordinates. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given (Note 1): * PV d(3,2) pv-vector (AU, AU/day) * * Returned (Note 2): * RA d right ascension (radians) * DEC d declination (radians) * PMR d RA proper motion (radians/year) * PMD d Dec proper motion (radians/year) * PX d parallax (arcsec) * RV d radial velocity (km/s, positive = receding) * J i status: * 0 = OK * -1 = superluminal speed (Note 5) * -2 = null position vector * * Notes: * * 1) The specified pv-vector is the coordinate direction (and its rate * of change) for the epoch at which the light leaving the star * reached the solar-system barycenter. * * 2) The star data returned by this routine are "observables" for an * imaginary observer at the solar-system barycenter. Proper motion * and radial velocity are, strictly, in terms of barycentric * coordinate time, TCB. For most practical applications, it is * permissible to neglect the distinction between TCB and ordinary * "proper" time on Earth (TT/TAI). The result will, as a rule, be * limited by the intrinsic accuracy of the proper-motion and radial- * velocity data; moreover, the supplied pv-vector is likely to be * merely an intermediate result (for example generated by the * routine iau_STARPV), so that a change of time unit will cancel * out overall. * * 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. * * Summarizing, the specified pv-vector is for most stars almost * identical to the result of applying the standard geometrical * "space motion" transformation to the catalog data. The * differences, which are the subject of the Stumpff paper cited * below, are: * * (i) In stars with significant radial velocity and proper motion, * the constantly changing light-time distorts the apparent proper * motion. Note that this is a classical, not a relativistic, * effect. * * (ii) The transformation complies with special relativity. * * 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; the radial velocity is in km/s, but * the pv-vector result is in AU and AU/day. * * 4) The proper motions are the rate of change of the right ascension * and declination at the catalog epoch and are in radians per Julian * year. The RA proper motion is in terms of coordinate angle, not * true angle, and will thus be numerically larger at high * declinations. * * 5) Straight-line motion at constant speed in the inertial frame is * assumed. If the speed is greater than or equal to the speed of * light, the routine aborts with an error status. * * 6) The inverse transformation is performed by the routine iau_STARPV. * * Called: * iau_PN decompose p-vector into modulus and direction * iau_PDP scalar product of two p-vectors * iau_SXP multiply p-vector by scalar * iau_PMP p-vector minus p-vector * iau_PM modulus of p-vector * iau_PPP p-vector plus p-vector * iau_PV2S pv-vector to spherical * iau_ANP normalize angle into range 0 to 2pi * * Reference: * * Stumpff, P., Astron.Astrophys. 144, 232-240 (1985). * * This revision: 2007 September 14 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION PV(3,2), RA, DEC, PMR, PMD, PX, RV INTEGER J * Julian years to days DOUBLE PRECISION Y2D PARAMETER ( Y2D = 365.25D0 ) * Radians to arcseconds DOUBLE PRECISION DR2AS PARAMETER ( DR2AS = 206264.8062470963551564734D0 ) * Days to seconds DOUBLE PRECISION D2S PARAMETER ( D2S = 86400D0 ) * AU (m) DOUBLE PRECISION AUM PARAMETER ( AUM = 149597870D3 ) * Speed of light (AU per day) DOUBLE PRECISION C PARAMETER ( C = D2S/499.004782D0 ) DOUBLE PRECISION R, X(3), VR, UR(3), VT, UT(3), BETT, BETR, D, W, : DEL, USR(3), UST(3), A, RAD, DECD, RD DOUBLE PRECISION iau_ANP * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Isolate the radial component of the velocity (AU/day, inertial). CALL iau_PN ( PV(1,1), R, X ) CALL iau_PDP ( X, PV(1,2), VR ) CALL iau_SXP ( VR, X, UR ) * Isolate the transverse component of the velocity (AU/day, inertial). CALL iau_PMP ( PV(1,2), UR, UT ) CALL iau_PM ( UT, VT ) * Special-relativity dimensionless parameters. BETT = VT / C BETR = VR / C * The inertial-to-observed correction terms. D = 1D0 + BETR W = 1D0 - BETR*BETR - BETT*BETT IF ( D.EQ.0D0 .OR. W.LT.0D0 ) THEN J = -1 GO TO 9 END IF DEL = SQRT(W) - 1D0 * Apply relativistic correction factor to radial velocity component. IF ( BETR.NE.0D0 ) THEN W = ( BETR-DEL ) / ( BETR*D ) ELSE W = 1D0 END IF CALL iau_SXP ( W, UR, USR ) * Apply relativistic correction factor to tangential velocity component. CALL iau_SXP ( 1D0/D, UT, UST ) * Combine the two to obtain the observed velocity vector (AU/day). CALL iau_PPP ( USR, UST, PV(1,2) ) * Cartesian to spherical. CALL iau_PV2S ( PV, A, DEC, R, RAD, DECD, RD ) IF ( R .EQ. 0D0 ) THEN J = -2 GO TO 9 END IF * Return RA in range 0 to 2pi. RA = iau_ANP ( A ) * Return proper motions in radians per year. PMR = RAD * Y2D PMD = DECD * Y2D * Return parallax in arcsec. PX = DR2AS / R * Return radial velocity in km/s. RV = 1D-3 * RD * AUM / D2S * OK status. J = 0 * Exit. 9 CONTINUE * Finished. *+---------------------------------------------------------------------- * * 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. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the 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. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "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 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. * * 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 * * *----------------------------------------------------------------------- END