int eraStarpm	(	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
	)

Definition at line 3 of file starpm.c.

References eraPdp(), eraPm(), eraPvstar(), eraPvu(), eraStarpv(), and ERFA_DC.

Referenced by eraPmsafe(), palPm(), and t_starpm().

{
   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 = eraStarpv(ra1, dec1, pmr1, pmd1, px1, rv1, pv1);

/* Light time when observed (days). */
   tl1 = eraPm(pv1[0]) / ERFA_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. */
   eraPvu(dt + tl1, pv1, pv);

/* From this geometric position, deduce the observed light time (days) */
/* at the "after" epoch (with theoretically unneccessary error check). */
   r2 = eraPdp(pv[0], pv[0]);
   rdv = eraPdp(pv[0], pv[1]);
   v2 = eraPdp(pv[1], pv[1]);
   c2mv2 = ERFA_DC*ERFA_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. */
   eraPvu(dt + (tl1 - tl2), pv1, pv2);

/* Space motion pv-vector to RA,Dec etc. at the "after" epoch. */
   j2 = eraPvstar(pv2, ra2, dec2, pmr2, pmd2, px2, rv2);

/* Final status. */
   j = (j2 == 0) ? j1 : -1;

   return j;

}

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