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muccc / iridium-toolkit

A set of tools to parse Iridium frames
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Satellite name doesn't match with Celestrak TLE data #28

Closed alper-d closed 2 years ago

alper-d commented 4 years ago

Hi! ra_sat field of RA message doesn't correspond to TLE file of Celestrak, and satellite monitoring (http://celestrak.com/NORAD/elements/). How should I handle that?

schneider42 commented 4 years ago

The SV number in the Ring Alert messages is a 7 bit field. Originally it simply contained the IRIDIUM XY number of Block 1 SVs.

With the introduction of Iridium Next, this field became to small (66 * 2 < 2**7), so Iridium started to reuse numbers of (de-activated / de-orbited) Block 1 SVs. This means that the SV number in the Ring Alert message does not equal the IRIDIUM XYZ number anymore.

We haven't looked into this anymore but it should be trivial to create a table which provides a mapping from SV number in the Ring Alert to "IRIDIUM XYZ" designation. Wanna try? ;)

Sec42 commented 2 years ago

I just pushed code to do this in 2e3d1aa5bcd6b8fc9bc51fae620442c600d73516.

You will need to install the python3 skyfield module and have TLE data in tracking/iridium-NEXT.txt - which you can fetch/update that by running cd tracking && ./update-tracking

Pipe some parsed IRA into reassembler.py -m satmap and it should output a mapping for those based on TLE data.

Please note that the TLE data and your received IRA frames need to be the same age. If they differ by more then a couple of days, accuracy of the mapping may be reduced.