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<?php |
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/** |
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* Ported from gpredict to PHP by Bill Shupp. License: GPL 2. |
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*/ |
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require_once 'Exception.php'; |
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/** |
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* Predict_TLE |
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* |
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* All routines for parsing and validating NORAD two line element sets |
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*/ |
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class Predict_TLE |
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{ |
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public $header; /* Header line of TLE file */ |
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public $line1; /* Line 1 of TLE */ |
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public $line2; /* Line 2 of TLE */ |
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public $epoch; /*!< Epoch Time in NORAD TLE format YYDDD.FFFFFFFF */ |
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public $epoch_year; /*!< Epoch: year */ |
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public $epoch_day; /*!< Epoch: day of year */ |
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public $epoch_fod; /*!< Epoch: Fraction of day. */ |
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public $xndt2o; /*!< 1. time derivative of mean motion */ |
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public $xndd6o; /*!< 2. time derivative of mean motion */ |
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public $bstar; /*!< Bstar drag coefficient. */ |
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public $xincl; /*!< Inclination */ |
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public $xnodeo; /*!< R.A.A.N. */ |
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public $eo; /*!< Eccentricity */ |
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public $omegao; /*!< argument of perigee */ |
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public $xmo; /*!< mean anomaly */ |
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public $xno; /*!< mean motion */ |
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public $catnr; /*!< Catalogue Number. */ |
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public $elset; /*!< Element Set number. */ |
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public $revnum; /*!< Revolution Number at epoch. */ |
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public $sat_name; /*!< Satellite name string. */ |
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public $idesg; /*!< International Designator. */ |
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public $status; /*!< Operational status. */ |
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/* values needed for squint calculations */ |
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public $xincl1; |
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public $xnodeo1; |
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public $omegao1; |
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/* Converts the strings in a raw two-line element set */ |
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/* to their intended numerical values. No processing */ |
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/* of these values is done, e.g. from deg to rads etc. */ |
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/* This is done in the select_ephemeris() function. */ |
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public function __construct($header, $line1, $line2) |
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{ |
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if (!$this->Good_Elements($line1, $line2)) { |
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throw new Predict_Exception('Invalid TLE contents'); |
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} |
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$this->header = $header; |
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$this->line1 = $line1; |
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$this->line2 = $line2; |
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/** Decode Card 1 **/ |
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/* Satellite's catalogue number */ |
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$this->catnr = (int) substr($line1, 2, 5); |
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/* International Designator for satellite */ |
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$this->idesg = substr($line1, 9, 8); |
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/* Epoch time; this is the complete, unconverted epoch. */ |
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/* Replace spaces with 0 before casting, as leading spaces are allowed */ |
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$this->epoch = (float) str_replace(' ', '0', substr($line1, 18, 14)); |
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/* Now, convert the epoch time into year, day |
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and fraction of day, according to: |
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YYDDD.FFFFFFFF |
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*/ |
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// Adjust for 2 digit year through 2056 |
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$this->epoch_year = (int) substr($line1, 18, 2); |
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if ($this->epoch_year > 56) { |
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$this->epoch_year = $this->epoch_year + 1900; |
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} else { |
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$this->epoch_year = $this->epoch_year + 2000; |
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} |
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/* Epoch day */ |
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$this->epoch_day = (int) substr($line1, 20, 3); |
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/* Epoch fraction of day */ |
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$this->epoch_fod = (float) substr($line1, 23, 9); |
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/* Satellite's First Time Derivative */ |
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$this->xndt2o = (float) substr($line1, 33, 10); |
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/* Satellite's Second Time Derivative */ |
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$this->xndd6o = (float) (substr($line1, 44, 1) . '.' . substr($line1, 45, 5) . 'E' . substr($line1, 50, 2)); |
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/* Satellite's bstar drag term |
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FIXME: How about buff[0] ???? |
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*/ |
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$this->bstar = (float) (substr($line1, 53, 1) . '.' . substr($line1, 54, 5) . 'E' . substr($line1, 59, 2)); |
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/* Element Number */ |
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$this->elset = (int) substr($line1, 64, 4); |
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/** Decode Card 2 **/ |
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/* Satellite's Orbital Inclination (degrees) */ |
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$this->xincl = (float) substr($line2, 8, 8); |
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/* Satellite's RAAN (degrees) */ |
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$this->xnodeo = (float) substr($line2, 17, 8); |
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/* Satellite's Orbital Eccentricity */ |
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$this->eo = (float) ('.' . substr($line2, 26, 7)); |
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/* Satellite's Argument of Perigee (degrees) */ |
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$this->omegao = (float) substr($line2, 34, 8); |
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/* Satellite's Mean Anomaly of Orbit (degrees) */ |
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$this->xmo = (float) substr($line2, 43, 8); |
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/* Satellite's Mean Motion (rev/day) */ |
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$this->xno = (float) substr($line2, 52, 11); |
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/* Satellite's Revolution number at epoch */ |
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$this->revnum = (float) substr($line2, 63, 5); |
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} |
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/* Calculates the checksum mod 10 of a line from a TLE set and */ |
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/* returns true if it compares with checksum in column 68, else false.*/ |
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/* tle_set is a character string holding the two lines read */ |
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/* from a text file containing NASA format Keplerian elements. */ |
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/* NOTE!!! The stuff about two lines is not quite true. |
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The function assumes that tle_set[0] is the begining |
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of the line and that there are 68 elements - see the consumer |
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*/ |
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public function Checksum_Good($tle_set) |
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{ |
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if (strlen($tle_set) < 69) { |
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return false; |
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} |
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$checksum = 0; |
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for ($i = 0; $i < 68; $i++) { |
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if (($tle_set[$i] >= '0') && ($tle_set[$i] <= '9')) { |
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$value = $tle_set[$i] - '0'; |
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} else if ($tle_set[$i] == '-' ) { |
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$value = 1; |
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} else { |
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$value = 0; |
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} |
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$checksum += $value; |
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} |
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$checksum %= 10; |
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$check_digit = $tle_set[68] - '0'; |
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return $checksum == $check_digit; |
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} |
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/* Carries out various checks on a TLE set to verify its validity */ |
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/* $line1 is the first line of the TLE, $line2 is the second line */ |
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/* from a text file containing NASA format Keplerian elements. */ |
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public function Good_Elements($line1, $line2) |
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{ |
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/* Verify checksum of both lines of a TLE set */ |
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if (!$this->Checksum_Good($line1) || !$this->Checksum_Good($line2)) { |
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return false; |
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} |
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/* Check the line number of each line */ |
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if (($line1[0] != '1') || ($line2[0] != '2')) { |
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return false; |
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} |
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/* Verify that Satellite Number is same in both lines */ |
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if (strncmp($line1[2], $line2[2], 5) != 0) { |
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return false; |
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} |
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/* Check that various elements are in the right place */ |
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if (($line1[23] != '.') || |
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($line1[34] != '.') || |
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($line2[11] != '.') || |
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($line2[20] != '.') || |
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($line2[37] != '.') || |
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($line2[46] != '.') || |
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($line2[54] != '.') || |
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(strncmp(substr($line1, 61), ' 0 ', 3) != 0)) { |
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return false; |
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} |
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return true; |
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} |
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/** |
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* A function to allow checksum creation of a line. This is driven by |
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* the fact that some TLEs from SpaceTrack are missing checksum numbers. |
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* You can use this to create a checksum for a line, but you should |
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* probably have confidence that the TLE data itself is good. YMMV. |
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* |
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* @throws Predict_Exception if the line is not exactly 68 chars |
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* @return string |
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*/ |
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static public function createChecksum($line) |
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{ |
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if (strlen($line) != 68) { |
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throw Predict_Exception('Invalid line, needs to e 68 chars'); |
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} |
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$checksum = 0; |
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for ($i = 0; $i < 68; $i++) { |
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if (($line[$i] >= '0') && ($line[$i] <= '9')) { |
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$value = (int) $line[$i]; |
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} else if ($line[$i] == '-' ) { |
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$value = 1; |
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} else { |
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$value = 0; |
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} |
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$checksum += $value; |
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} |
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$checksum %= 10; |
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return $checksum; |
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} |
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} |
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Ysurac /
FlightAirMap
