Observation 2244782: LUSAT (20442)

Regarding Observation 2244782

How do I vet this ? There is an obvious strong carrier which has been corrected for Doppler but it caries no modulation. I would guess it’s faulty therefore should be vetted as bad?

If it is clearly a signal from the satellite (which it is), then it should be vetted as good. Remember, good/bad is all about ‘is the satellite alive’. (admittedly in this case the satellite might be a zombie…).

Mark VK5QI


This one is pretty simple. A check of recent “good” observations of this satellite all show the same thing (a rock solid unmodulated carrier). “good”.

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Thanks. I think I got it now. It’s not a case of good or bad but rather a case of dead or alive. If the satellite is transmitting a bad signal, it’s still good.

So what do we do about the ISS. If it’s not transmitting APRS beacons but we know it’s still up there ‘alive’, is it automatically good even though it’s not transmitting? I’d say no signal and I know my station is not faulty then it’s bad. Confusing??

It’s not exactly dead or alive, but it’s there is signal (broken or not) or there isn’t.

So, in your ISS example, if you see/hear APRS Beacons is good if not then no signal = bad. In the bad situation, there are 2 different meanings, either the satellite wasn’t transmitting at that time or the station wasn’t able to catch it during that pass (for example due to low elevation).

The concept is that with many observations, statistically, you will be able to find out if satellite’s transmitter is alive or not and if a station works fine or not and for which passes.

I got it on normal satellite but
the ISS no signal=bad example.
I hear no signal but I know my station is OK because I just heard another satellite and I know the ISS is working and has a nice high pass, because I saw/heard APRS beacons on the previous pass so is it still bad?

I’m not trying to be difficult but you can understand why I’m a little confused. I tend to agree a good pass but no signal = bad. Any Doppler corrected signal down the middle=good.

My concern is, will this give the ISS APRS station a bad reputation even though it doesn’t deserve it.

I often look at the satellite’s pass elevation and it’s ratio red to green, when I schedule an observation. If others do this as well this would skew the green/red ratio because less people would schedule red satellites.

Damn statistics, hi hi

It is bad. Think of it in a different way, you are a researcher that wants to do some research on the APRS signals from ISS, how are you going to find which observations to use?

Indeed the current stats are not always fair or useful (for both stations and satellites/transmitters), we need to have more stats, for example one could be how much active is the satellite the last 10 days or other similar indicators. If I don’t make a mistake, there is an issue for adding more stats and also check using the grafana dashboards in the future.

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Lots of people would disagree… the ISS digipeater is a mess (which is why it’s being replaced soon). It turns on and off seemingly by itself. One day it hears wonderfully, the next day nobody can get in. And have you ever looked at an actual packet? The transmitter drifts about a kHz during the packet, so the packets are “slanted” - making decoding just a little bit more difficult. :slight_smile:

But that is besides the point. A better way to look at the “Good/Bad” is replace “good” with “observed” and “bad” with “not observed”. That is how the SatNogs network actually treats the observations.

Thanks for the update. Well that sure explains why I can see and hear the packets from the ISS with my SDRPlay and SDRuno but direwolf doesn’t decode sometimes. This combo seems more sensitive than my SatNOGS RPi & RTL-SDR stations.

Observed or not observed makes more sense because after practicing a while, I can now tell, just by looking at the waterfall, If the satellite is transmitting or not.