int DLL_FUNC SGP4( const double tsince, const tle_t *tle, const double *params,
double *pos, double *vel)
{
double
a, e, omega, omgadf,
temp, tempa, tempe, templ, tsq,
xl, xmdf, xmp, xnoddf, xnode;
/* Update for secular gravity and atmospheric drag. */
xmdf = tle->xmo+p_xmdot*tsince;
omgadf = tle->omegao+p_omgdot*tsince;
xnoddf = tle->xnodeo+p_xnodot*tsince;
omega = omgadf;
xmp = xmdf;
tsq = tsince*tsince;
xnode = xnoddf+xnodcf*tsq;
tempa = 1-c1*tsince;
tempe = tle->bstar*c4*tsince;
templ = t2cof*tsq;
if( !simple_flag)
{
const double delomg = omgcof*tsince;
double delm = 1. + p_eta * cos(xmdf);
double tcube, tfour;
delm = xmcof * (delm * delm * delm - delmo);
temp = delomg+delm;
xmp = xmdf+temp;
omega = omgadf-temp;
tcube = tsq*tsince;
tfour = tsince*tcube;
tempa = tempa-d2*tsq-d3*tcube-d4*tfour;
tempe = tempe+tle->bstar*c5*(sin(xmp)-sinmo);
templ = templ+t3cof*tcube+tfour*(t4cof+tsince*t5cof);
}; /* End of if (isFlagClear(SIMPLE_FLAG)) */
a = p_aodp*tempa*tempa;
e = tle->eo-tempe;
/* A highly arbitrary lower limit on e, of 1e-6: */
if( e < ECC_EPS)
e = ECC_EPS;
xl = xmp+omega+xnode+p_xnodp*templ;
if( tempa < 0.) /* force negative a, to indicate error condition */
a = -a;
return( sxpx_posn_vel( xnode, a, e, p_cosio, p_sinio, tle->xincl,
omega, xl, pos, vel));
} /*SGP4*/
void DLL_FUNC SDP4( const double tsince, const tle_t *tle, const double *params,
double *pos, double *vel)
{
double
a, tempa, tempe, templ, tsq,
xl, xmam, xmdf, xnoddf;
/* Update for secular gravity and atmospheric drag */
xmdf = tle->xmo+deep_arg->xmdot*tsince;
deep_arg->omgadf = tle->omegao+deep_arg->omgdot*tsince;
xnoddf = tle->xnodeo+deep_arg->xnodot*tsince;
tsq = tsince*tsince;
deep_arg->xnode = xnoddf+xnodcf*tsq;
tempa = 1-c1*tsince;
tempe = tle->bstar*c4*tsince;
templ = t2cof*tsq;
deep_arg->xn = deep_arg->xnodp;
/* Update for deep-space secular effects */
deep_arg->xll = xmdf;
deep_arg->t = tsince;
Deep_dpsec( tle, deep_arg);
xmdf = deep_arg->xll;
a = pow(xke/deep_arg->xn,two_thirds)*tempa*tempa;
deep_arg->em = deep_arg->em-tempe;
xmam = xmdf+deep_arg->xnodp*templ;
/* Update for deep-space periodic effects */
deep_arg->xll = xmam;
Deep_dpper( deep_arg);
xmam = deep_arg->xll;
xl = xmam + deep_arg->omgadf + deep_arg->xnode;
sxpx_posn_vel( deep_arg->xnode, a, deep_arg->em, params, deep_arg->cosio,
deep_arg->sinio, deep_arg->xinc, deep_arg->omgadf,
xl, pos, vel);
} /* SDP4 */
