What's a Two Line Element Set (TLE)?

A two line element set (TLE) is a group of numbers provided in two lines and separated by spaces, that specify the orbital parameters (elements) for a satellite, spent booster rocket, or other man-made satellites.

A Typical TLE, and what the numbers are:

ISS (ZARYA)             
1 25544U 98067A   02166.25000000  .00022749  00000-0  30765-3 0  5637
2 25544  51.6332  62.6174 0006804 238.6710  31.2451 15.57611327203721

NAME             
1 [IDXXXU] [Int Desig] [Epoch] [FTD MM] [STD MM] [drag] [Eph T] [Ele #] 
2 [IDXXXX]     [Inc]     [RA AN]     [Ecc]     [AOP]    [MA]       [Revs]+[ON]

Note: Not all these numbers are needed for programming your Autostar manually. Downloadable TLE's can be imported into the Autostar using the Meade #505 cable or equivalent, and the Autostar update software.

TLE Name

ISS (Zarya)  - International Space Station, (Zarya Module)

Line One
1 25544U 98067A 02166.25000000 .00022749 00000-0 30765-3 0 5637
1 [IDXXXU] [Int Desig] [Epoch] [FTD MM] [STD MM] [drag] [Eph T] [Ele #]

ID = Satellite Number - 25544U (U=unclassified)

Int Desig = International Designation (date lauched, launch number of year, section) - 98067A

Epoch = Year (last two digits) , day of year, and fractional day - 2002, day 166.25000000

FTD MM= First Time Derivative of Mean Motion - .00022749

STD MM= Second Time Derivative of Mean Motion - 00000-0

drag = BSTAR drag term (decimal assumed) - 30765-3

Eph T = Ephemeris Type - 0

Ele # = Element Number - 5637

Line Two
2 25544 51.6332 62.6174 0006804 238.6710 31.2451 15.57611327203721
2 [IDXXXX] [Inc] [RA AN] [Ecc] [AOP] [MA] [Revs]+[ON]

ID = Satellite Number - 25544

Inc = Inclination (degrees) - 51.6332

RA AN = Right Ascension of Ascending Node (degrees) - 62.6174

Ecc = Eccentricity (decimal assumed) - .0006804

AOP = Argument of Perigree (degrees) - 238.6710

MA = Mean Anomaly (degrees) - 31.2451

Revs = Revolutions per day - 15.57611327

ON = Orbit Number at Epoch - 20372(.)1

What's "AOS"?
That's "Aquisition of Signal", or when and where the Autostar will first "see" the satellite above the horizon. Newer firmware (from 25.Ea forward) allows you to edit the AOS horizon (if you have trees or other obstructions in the way) or older firmware with Dick Seymour's Autostar patches.

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