public static function Sat_Eclipsed(Predict_Vector $pos, Predict_Vector $sol, &$depth)
{
$Rho = new Predict_Vector();
$earth = new Predict_Vector();
/* Determine partial eclipse */
$sd_earth = Predict_Math::ArcSin(Predict::xkmper / $pos->w);
Predict_Math::Vec_Sub($sol, $pos, $Rho);
$sd_sun = Predict_Math::ArcSin(Predict::__sr__ / $Rho->w);
Predict_Math::Scalar_Multiply(-1, $pos, $earth);
$delta = Predict_Math::Angle($sol, $earth);
$depth = $sd_earth - $sd_sun - $delta;
if ($sd_earth < $sd_sun) {
return 0;
} else {
if ($depth >= 0) {
return 1;
} else {
return 0;
}
}
}
/**
* Experimental attempt at calculating apparent magnitude. Known intrinsic
* magnitudes are listed inside the function for now.
*
* @param float $time The daynum the satellite is calculated for
* @param Predict_QTH $qth The observer location
*
* @return null on failure, float otherwise
*/
public function calculateApparentMagnitude($time, Predict_QTH $qth)
{
// Recorded intrinsic magnitudes and their respective
// illumination and distance from heavens-above.com
static $intrinsicMagnitudes = array('25544' => array('mag' => -1.3, 'illum' => 0.5, 'distance' => 1000));
// Return null if we don't have a record of the intrinsic mag
if (!isset($intrinsicMagnitudes[$this->tle->catnr])) {
return null;
}
$imag = $intrinsicMagnitudes[$this->tle->catnr];
// Convert the observer's geodetic info to radians and km so
// we can compare vectors
$observerGeo = new Predict_Geodetic();
$observerGeo->lat = Predict_Math::Radians($qth->lat);
$observerGeo->lon = Predict_Math::Radians($qth->lon);
$observerGeo->alt = $qth->alt * 1000;
// Now determine the sun and observer positions
$observerPos = new Predict_Vector();
$observerVel = new Predict_Vector();
$solarVector = new Predict_Vector();
Predict_Solar::Calculate_Solar_Position($time, $solarVector);
Predict_SGPObs::Calculate_User_PosVel($time, $observerGeo, $observerPos, $observerVel);
// Determine the solar phase and and thus the percent illumination
$observerSatPos = new Predict_Vector();
Predict_Math::Vec_Sub($this->pos, $observerPos, $observerSatPos);
$phaseAngle = Predict_Math::Degrees(Predict_Math::Angle($solarVector, $observerSatPos));
$illum = $phaseAngle / 180;
$illuminationChange = $illum / $imag['illum'];
$inverseSquareOfDistanceChange = pow($imag['distance'] / $this->range, 2);
$changeInMagnitude = log($illuminationChange * $inverseSquareOfDistanceChange, self::POGSONS_RATIO);
return $imag['mag'] - $changeInMagnitude;
}
