void eraRefco	(	double	phpa,
		double	tc,
		double	rh,
		double	wl,
		double *	refa,
		double *	refb
	)

Definition at line 3 of file refco.c.

References ERFA_GMAX, ERFA_GMIN, and t.

Referenced by eraApco13(), eraApio13(), palRefcoq(), and t_refco().

{
   int optic;
   double p, t, r, w, ps, pw, tk, wlsq, gamma, beta;

/* Decide whether optical/IR or radio case:  switch at 100 microns. */
   optic = ( wl <= 100.0 );

/* Restrict parameters to safe values. */
   t = ERFA_GMAX ( tc, -150.0 );
   t = ERFA_GMIN ( t, 200.0 );
   p = ERFA_GMAX ( phpa, 0.0 );
   p = ERFA_GMIN ( p, 10000.0 );
   r = ERFA_GMAX ( rh, 0.0 );
   r = ERFA_GMIN ( r, 1.0 );
   w = ERFA_GMAX ( wl, 0.1 );
   w = ERFA_GMIN ( w, 1e6 );

/* Water vapour pressure at the observer. */
   if ( p > 0.0 ) {
      ps = pow ( 10.0, ( 0.7859 + 0.03477*t ) /
                          ( 1.0 + 0.00412*t ) ) *
                 ( 1.0 + p * ( 4.5e-6 + 6e-10*t*t )  );
      pw = r * ps / ( 1.0 - (1.0-r)*ps/p );
   } else {
      pw = 0.0;
   }

/* Refractive index minus 1 at the observer. */
   tk = t + 273.15;
   if ( optic ) {
      wlsq = w * w;
      gamma = ( ( 77.53484e-6 +
                 ( 4.39108e-7 + 3.666e-9/wlsq ) / wlsq ) * p
                    - 11.2684e-6*pw ) / tk;
   } else {
      gamma = ( 77.6890e-6*p - ( 6.3938e-6 - 0.375463/tk ) * pw ) / tk;
   }

/* Formula for beta from Stone, with empirical adjustments. */
   beta = 4.4474e-6 * tk;
   if ( ! optic ) beta -= 0.0074 * pw * beta;

/* Refraction constants from Green. */
   *refa = gamma * ( 1.0 - beta );
   *refb = - gamma * ( beta - gamma / 2.0 );

/* Finished. */

}

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