Scan motor current is going up again, maybe it will fix?
this post was submitted on 13 Oct 2023
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Amateur Satellites
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Discussion about amateur reception and processing of data from artificial satellites, primarily through radio signals but data from internet resources is welcome too.
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Wow. Where are the artefacts coming from? Why is the analog transmission still active if digital is also available?
Also, the vertical lines in your image look suspicious. Is this a result of your software interpolating lines?
The satellite has a malfunction. The imager scans the planet one line at a time and the motor that scans it is stuck, and causing the motor to spin too slow. I'm not sure on the specifics, but the onboard computer ends up sending broken data, resulting in the artefacts in this image and the analog version.
The analog transmission is there for compatibility with old ground stations. It's much easier to receive, so cheap ground stations can be set up in places that don't have the money for a dish and rotor setup. The last satellite with the analog transmission was launched in 2009, all US satellites since have been only digital, and even removed the HRPT and replaced it with a much higher rate, harder to recive downlink.
Russian satellites have a digital signal at the same lower frequency instead of the analog signal for the same reason, but it looks much better because it is digital.
The image is the data as it was sent by the satellite, the vertical lines are probably coming from the satellite computer getting confused by the stuck scan motor.
Oh. I thought the analog scanner and digital imager were separate, and didn't realize that the analog signal had been digitally processed already.