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// Two-line satellite orbital element calculations.
//
// See:
// http://celestrak.com/columns/v04n03/index.asp#FAQ01
// and
// http://satobs.org/element.html
// and
// http://www.zeptomoby.com/satellites/
//
//
// Elements are of the format:
//
// SATNAME
// 1 NNNNNC NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
// 2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN
//
// A sample for the International Space Station:
//
// ISS
// 1 25544U 98067A 06153.51583746 .00020000 00000-0 20000-3 0 9003
// 2 25544 51.6326 263.0272 0009318 279.9714 80.0399 15.75882122 30853
class TLE
{
// A human-readable name
var name
// The NORAD catalog number
var catalogNumber
// Security classification of satellite
var securityClassification
// International COSPAR identification
var COSPAR
// The epoch year
// var epochYear
// The epoch day
// var epochDay
// The time that the satellite crossed the equator in a northerly direction.
var epoch
// First derivative of the mean motion
var meanMotion1
// Second derivative of the mean motion
var meanMotion2
// BStar drag term
var bStar
// Ephemeris type
var ephemerisType
// Element number
var elementNumber
// Inclination angle
var inclination
// Right ascension of ascending node
var rightAscension
// Eccentricity of orbit
var eccentricity
// Argument of perigee
var argumentOfPerigee
// Mean anomaly
var meanAnomaly
// Revolutions per day
var revolutionsPerDay
// Revolution number at epoch
var revolutionAtEpoch
// Constructor, parses a TLE specification from strings
new[readableName, line1, line2] :=
{
name = readableName
// Parse line 1
catalogNumber = trim[substrLen[line1, 2,5]]
securityClassification = substrLen[line1, 7,1]
COSPAR = trim[substrLen[line1, 9,8]]
year = parseInt[substrLen[line1, 18,2]]
if (year >= 57)
epochYear = year + 1900
else
epochYear = year + 2000
epochDay = eval[substrLen[line1, 20,12]]
epoch = parseDate["$epochYear GMT"] + epochDay days
meanMotion1 = eval[substrLen[line1, 33,10]]
meanMotion2 = eval[substrLen[line1, 44, 1] + "0." + substrLen[line1, 45,5] + "*10^" + substrLen[line1, 50,2]]
bStar = eval[substrLen[line1, 53, 1] + "0." + substrLen[line1, 54,5] + "*10^" + substrLen[line1, 59,2]]
ephemerisType = substrLen[line1, 62,1]
elementNumber = eval[substrLen[line1, 64,4]]
// Parse line 2
if (catalogNumber != trim[substrLen[line2, 2, 5]])
println["Error! catalog number does not match in lines 1 and 2!"]
// TODO: Throw an exception for the above.
inclination = eval[substrLen[line2, 8, 8]]
rightAscension = eval[substrLen[line2, 17, 8]]
eccentricity = eval["0." + substrLen[line2, 26, 7]]
argumentOfPerigee = eval[substrLen[line2, 34, 8]]
meanAnomaly = eval[substrLen[line2, 43, 8]]
revolutionsPerDay = eval[substrLen[line2, 52, 11]]
revolutionAtEpoch = eval[substrLen[line2, 63, 5]]
}
// Returns the orbital period
getOrbitalPeriod[] := day / revolutionsPerDay
}
line1Pattern = %r/1 # Line number 1
\s
(\d{1,5}) # Satellite number
(\w) # Designation
\s+
(\d{5}) # International designator
(\w{1,3}) # Designator parts
\s+
(\d{2}) # Epoch year (last 2 digits)
(\d{3}\.\d{8}) # Epoch day
\s+
((?:\+|\-)?\.\d{8}) # First derivative of mean motion
\s+
((?:\+|\-)?\S+) # Second derivative of mean motion
\s+
(\S+) # Bstar drag term
/x
line2Pattern = %r/^2 /
var name
var line1
var t
for line = lines["file:tletest.txt"]
{
if line =~ line1Pattern
line1 = line
else
if line =~ line2Pattern
{
t = new TLE[name, line1, line]
println[t]
println[t.epoch -> GMT]
} else
name = line
}
Download or view TLE.frink in plain text format
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Alan Eliasen was born 19966 days, 23 hours, 31 minutes ago.