| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | void slaH2fk5 ( double rh, double dh, double drh, double ddh,
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| 4 | double *r5, double *d5, double *dr5, double *dd5 )
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| 5 | /*
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| 6 | ** - - - - - - - - -
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| 7 | ** s l a H 2 f k 5
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| 8 | ** - - - - - - - - -
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| 9 | **
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| 10 | ** Transform Hipparcos star data into the FK5 (J2000) system.
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| 11 | **
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| 12 | ** (double precision)
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| 13 | **
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| 14 | ** This routine transforms Hipparcos star positions and proper
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| 15 | ** motions into FK5 J2000.
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| 16 | **
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| 17 | ** Given (all Hipparcos, epoch J2000):
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| 18 | ** rh double RA (radians)
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| 19 | ** dh double Dec (radians)
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| 20 | ** drh double proper motion in RA (dRA/dt, rad/Jyear)
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| 21 | ** ddh double proper motion in Dec (dDec/dt, rad/Jyear)
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| 22 | **
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| 23 | ** Returned (all FK5, equinox J2000, Epoch J2000):
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| 24 | ** r5 double RA (radians)
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| 25 | ** d5 double Dec (radians)
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| 26 | ** dr5 double proper motion in RA (dRA/dt, rad/Jyear)
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| 27 | ** dd5 double proper motion in Dec (dDec/dt, rad/Jyear)
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| 28 | **
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| 29 | ** Called: slaDs2c6, slaDav2m, slaDmxv, slaDimxv, slaDvxv,
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| 30 | ** slaDc62s, slaDranrm
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| 31 | **
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| 32 | ** Notes:
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| 33 | **
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| 34 | ** 1) The proper motions in RA are dRA/dt rather than
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| 35 | ** cos(Dec)*dRA/dt, and are per year rather than per century.
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| 36 | **
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| 37 | ** 2) The FK5 to Hipparcos transformation consists of a pure
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| 38 | ** rotation and spin; zonal errors in the FK5 catalogue are
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| 39 | ** not taken into account.
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| 40 | **
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| 41 | ** 3) The published orientation and spin components are interpreted
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| 42 | ** as "axial vectors". An axial vector points at the pole of the
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| 43 | ** rotation and its length is the amount of rotation in radians.
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| 44 | **
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| 45 | ** 4) See also slaFk52h, slaFk5hz, slaHfk5z.
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| 46 | **
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| 47 | ** Reference:
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| 48 | **
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| 49 | ** M.Feissel & F.Mignard, Astron. Astrophys. 331, L33-L36 (1998).
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| 50 | **
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| 51 | ** Last revision: 22 June 1999
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| 52 | **
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| 53 | ** Copyright P.T.Wallace. All rights reserved.
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| 54 | */
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| 55 |
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| 56 | #define AS2R 0.484813681109535994e-5 /* arcseconds to radians */
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| 57 |
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| 58 | {
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| 59 | /* FK5 to Hipparcos orientation and spin (radians, radians/year) */
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| 60 | static double ortn[3] = { -19.9e-3 * AS2R,
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| 61 | -9.1e-3 * AS2R,
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| 62 | 22.9e-3 * AS2R },
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| 63 | s5[3] = { -0.30e-3 * AS2R,
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| 64 | 0.60e-3 * AS2R,
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| 65 | 0.70e-3 * AS2R };
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| 66 |
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| 67 | double pvh[6], r5h[3][3], sh[3], vv[3], pv5[6], w, r, v;
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| 68 | int i;
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| 69 |
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| 70 |
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| 71 | /* Hipparcos barycentric position/velocity 6-vector (normalized). */
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| 72 | slaDs2c6 ( rh, dh, 1.0, drh, ddh, 0.0, pvh );
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| 73 |
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| 74 | /* FK5 to Hipparcos orientation matrix. */
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| 75 | slaDav2m ( ortn, r5h );
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| 76 |
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| 77 | /* Rotate the spin vector into the Hipparcos frame. */
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| 78 | slaDmxv ( r5h, s5, sh );
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| 79 |
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| 80 | /* De-orient & de-spin the 6-vector into FK5 J2000. */
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| 81 | slaDimxv ( r5h, pvh, pv5 );
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| 82 | slaDvxv ( pvh, sh, vv );
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| 83 | for ( i = 0; i < 3; i++ ) {
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| 84 | vv [ i ] = pvh [ i + 3 ] - vv [ i ];
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| 85 | }
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| 86 | slaDimxv ( r5h, vv, pv5 + 3 );
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| 87 |
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| 88 | /* FK5 6-vector to spherical. */
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| 89 | slaDc62s ( pv5, &w, d5, &r, dr5, dd5, &v );
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| 90 | *r5 = slaDranrm ( w );
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| 91 | }
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