From: tkelso@afit.af.mil (TS Kelso)
Subject: Two-Line Orbital Element Set Format
Apparently-To: sci-space-news@ames.arc.nasa.gov
Followup-To: sci.space
Keywords: Satellite, Orbital Elements, Keplerian, Format
Organization: Air Force Institute of Technology
Date: Fri, 2 Oct 1992 22:04:24 GMT

As a service to the satellite user community, the following description of the
NORAD two-line orbital element set format is uploaded to sci.space and
rec.radio.amateur.misc on a monthly basis.  The most current orbital elements
from the NORAD two-line element sets are carried on the Celestial BBS, (513)
427-0674, and are updated daily (when possible).  Documentation and tracking
software are also available on this system.  The Celestial BBS may be accessed
24 hours/day at 300, 1200, 2400, 4800, or 9600 bps using 8 data bits, 1 stop
bit, no parity.  In addition, element sets (also updated daily) and some
documentation and software are also available via anonymous ftp from
archive.afit.af.mil (129.92.1.66) in the directory pub/space.

==============================================================================

Data for each satellite consists of three lines in the following format:

AAAAAAAAAAA
1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN

Line 0 is a eleven-character name.

Lines 1 and 2 are the standard Two-Line Orbital Element Set Format identical
to that used by NORAD and NASA.  The format description is:

Line 1
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 10-11     International Designator (Last two digits of launch year)
 12-14     International Designator (Launch number of the year)
 15-17     International Designator (Piece of launch)
 19-20     Epoch Year (Last two digits of year)
 21-32     Epoch (Julian Day and fractional portion of the day)
 34-43     First Time Derivative of the Mean Motion
        or Ballistic Coefficient (Depending on ephemeris type)
 45-52     Second Time Derivative of Mean Motion (decimal point assumed;
           blank if N/A)
 54-61     BSTAR drag term if GP4 general perturbation theory was used.
           Otherwise, radiation pressure coefficient.  (Decimal point assumed)
 63-63     Ephemeris type
 65-68     Element number
 69-69     Check Sum (Modulo 10)
           (Letters, blanks, periods, plus signs = 0; minus signs = 1)

Line 2
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 09-16     Inclination [Degrees]
 18-25     Right Ascension of the Ascending Node [Degrees]
 27-33     Eccentricity (decimal point assumed)
 35-42     Argument of Perigee [Degrees]
 44-51     Mean Anomaly [Degrees]
 53-63     Mean Motion [Revs per day]
 64-68     Revolution number at epoch [Revs]
 69-69     Check Sum (Modulo 10)

All other columns are blank or fixed.

Example:

NOAA 6
1 11416U          86 50.28438588 0.00000140           67960-4 0  5293
2 11416  98.5105  69.3305 0012788  63.2828 296.9658 14.24899292346978
-- 
Dr TS Kelso                           Assistant Professor of Space Operations
tkelso@afit.af.mil                    Air Force Institute of Technology
Newsgroups: sci.space.news