<?php /** * An example of looking up the lat/lon of the sun for putting on a map. * "dark" lat/lon is the anti-solar point, useful for drawing a * "solar terminator" */ // No autoloading here, require needed files require_once 'Predict/Solar.php'; require_once 'Predict/SGPObs.php'; require_once 'Predict/Math.php'; require_once 'Predict/Time.php'; // Set up data constructs $solar_vector = new Predict_Vector(); $solar_geodetic = new Predict_Geodetic(); // Use current time in the form of a daynum $time = time(); $daynum = Predict_Time::unix2daynum($time); // Do calculations Predict_Solar::Calculate_Solar_Position($daynum, $solar_vector); Predict_SGPObs::Calculate_LatLonAlt($daynum, $solar_vector, $solar_geodetic); // Format to degrees $solar_lat = Predict_Math::Degrees($solar_geodetic->lat); $solar_lon = Predict_Math::Degrees($solar_geodetic->lon); // Reverse values for night circle center $dark_lat = -$solar_lat; $dark_lon = -$solar_lon; $output = array('solar_lat' => $solar_lat, 'solar_lon' => $solar_lon, 'dark_lat' => $dark_lat, 'dark_lon' => $dark_lon, 'timestamp' => $time); // output results var_dump(json_encode($output));
/** * Finds the current location of the sun based on the observer location * * @param Predict_QTH $qth The observer location * @param int $daynum The daynum or null to use the current daynum * * @return Predict_ObsSet */ public static function FindSun(Predict_QTH $qth, $daynum = null) { if ($daynum === null) { $daynum = Predict_Time::get_current_daynum(); } $obs_geodetic = new Predict_Geodetic(); $obs_geodetic->lon = $qth->lon * Predict::de2ra; $obs_geodetic->lat = $qth->lat * Predict::de2ra; $obs_geodetic->alt = $qth->alt / 1000.0; $obs_geodetic->theta = 0; $solar_vector = new Predict_Vector(); $zero_vector = new Predict_Vector(); $solar_set = new Predict_ObsSet(); self::Calculate_Solar_Position($daynum, $solar_vector); Predict_SGPObs::Calculate_Obs($daynum, $solar_vector, $zero_vector, $obs_geodetic, $solar_set); $solar_set->az = Predict_Math::Degrees($solar_set->az); $solar_set->el = Predict_Math::Degrees($solar_set->el); return $solar_set; }
/** SGP4SDP4 driver for doing AOS/LOS calculations. * @param Predict_Sat $sat The satellite data. * @param Predict_QTH $qth The QTH observer location data. * @param float $t The time for calculation (Julian Date) * */ public function predict_calc(Predict_Sat $sat, Predict_QTH $qth, $t) { $obs_set = new Predict_ObsSet(); $sat_geodetic = new Predict_Geodetic(); $obs_geodetic = new Predict_Geodetic(); $obs_geodetic->lon = $qth->lon * self::de2ra; $obs_geodetic->lat = $qth->lat * self::de2ra; $obs_geodetic->alt = $qth->alt / 1000.0; $obs_geodetic->theta = 0; $sat->jul_utc = $t; $sat->tsince = ($sat->jul_utc - $sat->jul_epoch) * self::xmnpda; /* call the norad routines according to the deep-space flag */ $sgpsdp = Predict_SGPSDP::getInstance($sat); if ($sat->flags & Predict_SGPSDP::DEEP_SPACE_EPHEM_FLAG) { $sgpsdp->SDP4($sat, $sat->tsince); } else { $sgpsdp->SGP4($sat, $sat->tsince); } Predict_Math::Convert_Sat_State($sat->pos, $sat->vel); /* get the velocity of the satellite */ $sat->vel->w = sqrt($sat->vel->x * $sat->vel->x + $sat->vel->y * $sat->vel->y + $sat->vel->z * $sat->vel->z); $sat->velo = $sat->vel->w; Predict_SGPObs::Calculate_Obs($sat->jul_utc, $sat->pos, $sat->vel, $obs_geodetic, $obs_set); Predict_SGPObs::Calculate_LatLonAlt($sat->jul_utc, $sat->pos, $sat_geodetic); while ($sat_geodetic->lon < -self::pi) { $sat_geodetic->lon += self::twopi; } while ($sat_geodetic->lon > self::pi) { $sat_geodetic->lon -= self::twopi; } $sat->az = Predict_Math::Degrees($obs_set->az); $sat->el = Predict_Math::Degrees($obs_set->el); $sat->range = $obs_set->range; $sat->range_rate = $obs_set->range_rate; $sat->ssplat = Predict_Math::Degrees($sat_geodetic->lat); $sat->ssplon = Predict_Math::Degrees($sat_geodetic->lon); $sat->alt = $sat_geodetic->alt; $sat->ma = Predict_Math::Degrees($sat->phase); $sat->ma *= 256.0 / 360.0; $sat->phase = Predict_Math::Degrees($sat->phase); /* same formulas, but the one from predict is nicer */ //sat->footprint = 2.0 * xkmper * acos (xkmper/sat->pos.w); $sat->footprint = 12756.33 * acos(self::xkmper / (self::xkmper + $sat->alt)); $age = $sat->jul_utc - $sat->jul_epoch; $sat->orbit = floor(($sat->tle->xno * self::xmnpda / self::twopi + $age * $sat->tle->bstar * self::ae) * $age + $sat->tle->xmo / self::twopi) + $sat->tle->revnum - 1; }
/** * 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; }