this post was submitted on 30 Aug 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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APT image from NOAA-15, currently with AVHRR scanner motor malfunction, plus raw image, waterfall screenshot, audio sample and DSB images as bonus. (i.imgur.com)
submitted 1 year ago by [email protected] to c/amateursatellites
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The main image in post was decoded with WXtoIMG as both noaa-apt and SatDump fail to synchronize it correctly.

Unprocessed image from noaa-apt:

Compatibility image link

Waterfall:

Compatibility image link
There you can see some breaks, the noticeable horizontal lines.

Which sounds like so (note: the waterfall shown above isn't from the same time as audio):

Compatibility audio link

And the bonus, DSB images:

Compatibility image link
Channels 1-20 are left-to-right then bottom.

And also AVHRR scan motor current as of today:

Compatibility image link

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[–] [email protected] 3 points 1 year ago

Another interesting thing I noticed about these broken APT images is the channel B sync marker is repeated twice instead of the channel A marker. This is why the sync fails, and it makes a "tick tick" sound instead of the "tick tock" sound it normally makes.
I'd love to know what is causing this, but I think only NOAA knows what is going on with that.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

Wow, nevedel som, že satelity ešte stále vysielajú analógovo. Miliarda ľudí si musela vymeniť televízny prijímač a tisíce meteorológov stále ladí SSTV...

A čo sú tie zubaté šikmé hrany v horných rohoch obrazu?

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

Takto vysielajú už len staré satelity NOAA-15 (skener sa stále zasekáva), NOAA-18 a NOAA-19.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (2 children)

To je mi jasné, digitální vysílání bude několikanásobně efektivnější. Ale tyhle věci slyším poprvé: ten skener je pohyblivý optický senzor? Ty data o motoru jsi získal jak? Satelit je vysílá jako digitální hodnoty ve stejném pásmu?

Edit: Holy shit, NOAA-15 je jen 25 let starý. Tou dobou už přece existoval JPEG!

[–] [email protected] 1 points 1 year ago

Telemetria pochádza s tadiaľto: https://www.star.nesdis.noaa.gov/icvs/status_N15_AVHRR.php
Myslím že je to vysielané v DSB downlinku v rovnakom pásme.

JPEG mohol existovať, ale musela by sa vymeniť existujúca technika. Tieto satelity vysielajú aj HRPT, digitálne vysielanie v pásme L so 4x vyšším rozlíšením než APT v 5 kanáloch namiesto dvoch.
Info o príjme HRPT

JPEG kompresiu v pásme 137MHz využíva LRPT. LRPT aktuálne vysiela len Meteor-M No. 2-3 ktorý má bohužiaľ poškodenú anténu, takže signál je dosť kolísavý.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

By the way, do you see my other reply under this (your) comment? I correctly set the comment language to Slovak, so it's possible it got filtered out if you don't have it in the Lemmy language settings.

It's not even a good comment though (mine).

[–] [email protected] 2 points 1 year ago (2 children)

You should try satdump for the DSB, it can make some nice HIRS composites.

The scan motor current seems to be dropping, maybe it will fix itself again.

[–] [email protected] 2 points 1 year ago (1 children)

That is from SatDump, I just put it together in JointPics.
In this case there wasn't anything interesting looking, at least with the pre-set composites. But to be honest, I am not sure how to use that properly. Also what's with the vertical lines with NOAA-15? When I tried NOAA-19 I got OK results

(Channel 20)

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

That's really strange, I checked my HIRS images from NOAA 15 and I don't have any vertical lines, was there any nearby interference?
It only works in day, but ch20, ch20, ch20 + ch8 * 0.1 seems to make a nice natural looking colour composite on HIRS. It's a bit hard to see because of how low res the HIRS is, but it makes the land green and the oceans a dark blue.
My HIRS from that pass (low elevation here):

[–] [email protected] 2 points 1 year ago

Nope. I also had those lines when I tried before, so I thought it's something with the satellite. Maybe there is some interference. NOAA-19 uses different frequency for DSB. I'll have to try with NOAA-18 (and hope it doesn't cut off again), that should be on same frequency as NOAA-15. But I didn't notice any interference.

Thanks for that setting. That looks nice.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

Also, The top right of your APT image is very interesting, some of the actual corupted data seems to be getting into the APT

[–] [email protected] 1 points 1 year ago (1 children)

Does the embedded audio work for anyone? I think it’s not even an official Lemmy/Markdown feature.

[–] [email protected] 2 points 1 year ago (1 children)

It works in the default Lemmy web UI. I tried it with Opera (Android) and Firefox (Manjaro). It relies on the browser's media player.

There's still the link below it, for when it doesn't work, which I expect from most Lemmy clients and probably Kbin too.

[–] [email protected] 1 points 1 year ago

Oh, I didn't check if the compatibility link is any different, I assumed it was the same.

Of course you cannot embed an external site in a comment but the raw file does seem to work, in browsers at least.