TABLE OF CONTENTS The two-line orbital elements can be found at a number of Web sites. The National Oceanographic and Atmospheric Administration (NOAA) Web site, at http://www.noaa.gov/, is probably the most useful to start with because it contains a great deal of general information on polar orbiting satellites as well as weather satellites in the geostationary orbit. An explanation of the two-line elements can be found in the FAQs section by Dr. T. S. Kelso at http://celestrak.com/. The two-line elements can be downloaded directly from http://celestrak.com/NORAD/elements/, (but see App. D) a typical readout being:
1 22969U 94003A 94284.57233250 .00000051 00000-0 10000-3 0 1147
2 22969 82.5601 334.1434 0015195 339.6133 20.4393 13.16724605 34163
A description of each line follows:
| Name | Description | Units | Example | Field Format |
|---|---|---|---|---|
| LINNO | Line number of element data (always 1 for line 1) | None | 1 | X |
| SATNO | Satellite number | None | 22969 | XXXXX |
| U | Not applicable | None | X | |
| IDYR | International designator (last two digits of launch year) | Launch year | 94 | XX |
| IDLNO | International designator (launch number of the year) | None | 3 | XXX |
| EPYR | Epoch year (last two digits of the year) | Epoch year | 94 | XX |
| EPOCH | Epoch (Julian day and fractional portion of the day) | Day | 284.57233250 | XXX.XXXXXXXX |
| NDTO2 or BTERM | First time derivative of the mean motion or ballistic coefficient (depending on the ephemeris type) | Revolutions per day 2 or m 2/kg | 0.00000051 | .XXXXXXXX * |
| NDDOT 6 | Second time derivative of ... |
