basics.cpp

卫星计算码

#include <math.h>
#include "norad.h"
#include "norad_in.h"

/*------------------------------------------------------------------*/

/* FMOD2P */
double FMod2p( const double x)
{
   double rval = fmod( x, twopi);

   if( rval < 0.)
      rval += twopi;
   return( rval);
} /* fmod2p */

/*------------------------------------------------------------------*/

/* Selects the type of ephemeris to be used (SGP*-SDP*) */
int DLL_FUNC select_ephemeris( const tle_t *tle)
{
   double ao, xnodp, delo, a1, del1, r1, temp;
   int rval;

   /* Period > 225 minutes is deep space */
   a1 = pow( xke / tle->xno, two_thirds);
   r1 = cos(tle->xincl);
   temp = ck2 * 1.5 * (r1*r1*3.0-1.0) * pow( 1.0-tle->eo*tle->eo, -1.5);
   del1 = temp/(a1*a1);
   ao = a1 * (1.0 - del1 * (1./3. + del1 * (del1 * 1.654320987654321+1.0)));
   delo = temp/(ao*ao);
   xnodp = tle->xno / (delo + 1.0);

   /* Select a deep-space/near-earth ephemeris */
   /* If the object makes less than 6.4 revolutions around the earth... */
   if (twopi / (xnodp * xmnpda) >= (1. / 6.4))
      rval = 1;      /* yes,  it should be a deep-space (SDPx) ephemeris */
   else
      rval = 0;      /* no,  you can go with an SGPx ephemeris */
   return( rval);
} /* End of select_ephemeris() */

/*------------------------------------------------------------------*/