(This page is a work in progress. It will be complete once all of the individual values are described in full.)
The orbital elements of the satellites tracked by NORAD are supplied in a “Two Line Element” format. This data is sometimes referred to as “Keplerian Elements”.
Here is a sample for the International Space Station for today.
ISS (ZARYA) 1 25544U 98067A 09070.38837942 .00007697 00000-0 63677-4 0 4357 2 25544 51.6394 87.9530 0009582 111.8389 22.9968 15.71382598590567
My intention with this post is to not just tell you what each value is, but demonstrate exactly what they relate to. Click on the description field for an in-depth detailed description.
Title Line
| Field | Columns | Description | Example |
|---|---|---|---|
| 1 | 01-24 | Satellite Name | ISS (ZARYA) |
Line 1
| Field | Columns | Description | Example |
|---|---|---|---|
| 1 | 01-01 | Line number | 1 |
| 2 | 03-07 | Satellite number | 25544 |
| 3 | 08-08 | Classification | U |
| 4 | 10-11 | International Designator (Year) | 98 |
| 5 | 12-14 | International Designator (Launch number) | 067 |
| 6 | 15-17 | International Designator (Piece) | A |
| 7 | 19-20 | Epoch Year (Last two digits of year) | 09 |
| 8 | 21-32 | Epoch (Day of the year and fractional portion of the day) | 070.38837942 |
| 9 | 34-43 | First Time Derivative of the Mean Motion | .00007697 |
| 10 | 45-52 | Second Time Derivative of Mean Motion (decimal point assumed) | 00000-0 |
| 11 | 54-61 | BSTAR drag term (decimal point assumed) | 63677-4 |
| 12 | 63-63 | The number 0 (Originally this should have been “Ephemeris type”) | 0 |
| 13 | 65-68 | Element number | 435 |
| 14 | 69-69 | Checksum (Modulo 10) | 7 |
Line 2
| Field | Columns | Description | Example |
|---|---|---|---|
| 1 | 01-01 | Line number | 2 |
| 2 | 03-07 | Satellite number | 25544 |
| 3 | 09-16 | Inclination [Degrees] | 51.6394 |
| 4 | 18-25 | Right Ascension of the Ascending Node [Degrees] | 87.9530 |
| 5 | 27-33 | Eccentricity (decimal point assumed) | 0009582 |
| 6 | 35-42 | Argument of Perigee [Degrees] | 111.8389 |
| 7 | 44-51 | Mean Anomaly [Degrees] | 22.9968 |
| 8 | 53-63 | Mean Motion [Revs per day] | 15.71382598 |
| 9 | 64-68 | Revolution number at epoch [Revs] | 59056 |
| 10 | 69-69 | Checksum (Modulo 10) | 7 |
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