Hi SatNOGS I’m a video & installation artist nyethompson.net. I’m currently working on a project exploring our relationship with satellites. As part of this I made these images recently using SatNOGS observation data from the aged ISIS-1 - I see the signals in the waterfalls as a kind of ‘drawing’ by the satellite.
I know this is a really old satellite but can anyone explain to me why there was a short burst of observations with data at the end of 2020 and then nothing before or since?
The data in the observations are noise frames. Noise frame is a demodulated frame that contains noise. Depending of the satellite modulation, demodulation process can produce easier or not frames that coming from noise and not from actual data.
By the way I checked a couple of observations of this satellite and it seems that currently you can only see the carrier and not any actual data. The carrier is the straight line you see in waterfalls.
Hi @fredy thanks so much for your reply. Your explanation really helped me to understand the observations better. May I ask another question please. There are small dots alongside the carrier lines in two of the waterfalls, can you tell me what they are?
Hi - I suspect that the small dots alongside the ISIS-1 carrier in the first two waterfall screenshots you posted are artefacts from terrestrial interference. The radio band that the signal from ISIS-1 is present in is typically quite noisy.
I’m particularly interested in the traces of these old satellites from the 60s. And thanks for clarifying the small dots too. Why does the TRANSIT5B-5 produce so many lines in the waterfall - are they all carrier waves?
The waterfall is shifted by about 5 kHz in order to center it at one of the sidebands, the carrier wave which is the center of the signal is roughly around the -5 kHz point at the waterfall, then 5 kHz from the carrier on both sides is analog telemetry, which is what produces the sound specific to Transit, and then around 10 kHz from the carrier is the digital telemetry, that’s what looks like the two close parallel lines. Further out are just “mirror” images of the carrier and telemetry.
Oh really interesting - thanks for the diagram @dereksgc - its does make an intriguing sound
So despite TRANSIT5B-5 being nearly 60 years in orbit its still capable of producing all these signals. Would that be because its solar panels are still collecting a trickle of energy?
It would seem so. And not only that, other electronics inside the satellite must still be working otherwise the telemetry wouldn’t be present, and in fact when the telemetry is demodulated it still shows signs of correct framing and a binary counter, so at the very least the satellite can still count (for the most part).
Right now it appears that the signal strength of Transit went down considerably, so it is more difficult to receive (hopefully temporarily)
