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/* Sun - object - earth angles and distances.
* q (object), e (earth), and p (q minus e) are input vectors.
* The answers are posted in the following global locations:
*/
#include "kep.h"
double FAR SE; /* earth-sun distance */
double FAR SO; /* object-sun distance */
double FAR EO; /* object-earth distance */
double FAR pq; /* cosine of sun-object-earth angle */
double FAR ep; /* -cosine of sun-earth-object angle */
double FAR qe; /* cosine of earth-sun-object angle */
int angles( p, q, e )
double p[], q[], e[];
{
double a, b, s;
int i;
EO = 0.0;
SE = 0.0;
SO = 0.0;
pq = 0.0;
ep = 0.0;
qe = 0.0;
for( i=0; i<3; i++ )
{
a = e[i];
b = q[i];
s = p[i];
EO += s * s;
SE += a * a;
SO += b * b;
pq += s * b;
ep += a * s;
qe += b * a;
}
EO = sqrt(EO); /* Distance between Earth and object */
SO = sqrt(SO); /* Sun - object */
SE = sqrt(SE); /* Sun - earth */
/* Avoid fatality: if object equals sun, SO is zero. */
if( SO > 1.0e-12 )
{
pq /= EO*SO; /* cosine of sun-object-earth */
qe /= SO*SE; /* cosine of earth-sun-object */
}
ep /= SE*EO; /* -cosine of sun-earth-object */
return(0);
}
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