int eraStarpv	(	double	ra,
		double	dec,
		double	pmr,
		double	pmd,
		double	px,
		double	rv,
		double	pv[2][3]
	)

Definition at line 3 of file starpv.c.

References eraPdp(), eraPm(), eraPmp(), eraPn(), eraPpp(), eraS2pv(), eraSxp(), eraZp(), ERFA_DAU, ERFA_DAYSEC, ERFA_DC, ERFA_DJY, ERFA_DR2AS, and i.

Referenced by eraFk52h(), eraH2fk5(), eraStarpm(), and t_starpv().

{
/* Smallest allowed parallax */
   static const double PXMIN = 1e-7;

/* Largest allowed speed (fraction of c) */
   static const double VMAX = 0.5;

/* Maximum number of iterations for relativistic solution */
   static const int IMAX = 100;

   int i, iwarn;
   double w, r, rd, rad, decd, v, x[3], usr[3], ust[3],
          vsr, vst, betst, betsr, bett, betr,
          dd, ddel, ur[3], ut[3],
          d = 0.0, del = 0.0,       /* to prevent */
          odd = 0.0, oddel = 0.0,   /* compiler   */
          od = 0.0, odel = 0.0;     /* warnings   */

/* Distance (AU). */
   if (px >= PXMIN) {
      w = px;
      iwarn = 0;
   } else {
      w = PXMIN;
      iwarn = 1;
   }
   r = ERFA_DR2AS / w;

/* Radial velocity (AU/day). */
   rd = ERFA_DAYSEC * rv * 1e3 / ERFA_DAU;

/* Proper motion (radian/day). */
   rad = pmr / ERFA_DJY;
   decd = pmd / ERFA_DJY;

/* To pv-vector (AU,AU/day). */
   eraS2pv(ra, dec, r, rad, decd, rd, pv);

/* If excessive velocity, arbitrarily set it to zero. */
   v = eraPm(pv[1]);
   if (v / ERFA_DC > VMAX) {
      eraZp(pv[1]);
      iwarn += 2;
   }

/* Isolate the radial component of the velocity (AU/day). */
   eraPn(pv[0], &w, x);
   vsr = eraPdp(x, pv[1]);
   eraSxp(vsr, x, usr);

/* Isolate the transverse component of the velocity (AU/day). */
   eraPmp(pv[1], usr, ust);
   vst = eraPm(ust);

/* Special-relativity dimensionless parameters. */
   betsr = vsr / ERFA_DC;
   betst = vst / ERFA_DC;

/* Determine the inertial-to-observed relativistic correction terms. */
   bett = betst;
   betr = betsr;
   for (i = 0; i < IMAX; i++) {
      d = 1.0 + betr;
      del = sqrt(1.0 - betr*betr - bett*bett) - 1.0;
      betr = d * betsr + del;
      bett = d * betst;
      if (i > 0) {
         dd = fabs(d - od);
         ddel = fabs(del - odel);
         if ((i > 1) && (dd >= odd) && (ddel >= oddel)) break;
         odd = dd;
         oddel = ddel;
      }
      od = d;
      odel = del;
   }
   if (i >= IMAX) iwarn += 4;

/* Replace observed radial velocity with inertial value. */
   w = (betsr != 0.0) ? d + del / betsr : 1.0;
   eraSxp(w, usr, ur);

/* Replace observed tangential velocity with inertial value. */
   eraSxp(d, ust, ut);

/* Combine the two to obtain the inertial space velocity. */
   eraPpp(ur, ut, pv[1]);

/* Return the status. */
   return iwarn;

}

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