Full disc weather satellite images from GK-2A

Show off any of your RTL-SDR or cheap SDR related projects.
Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 3:52 am

In July of this year, Korea replaced it's ageing Coms-1 geostationary weather satellite with a brand new one called Geokompsat 2A or GK-2A for short. This satellite can be received directly on L band. The easiest transponder is the LRIT one on 1692.140 mHz. At first they carried a few different channels so colour images were possible, but unfortunately they now only have a single IR channel, though it is full disc at 2200x2200 resolution. If you want more channels there is always HRIT or Ultra HRIT but these need enormous dishes and more expensive receivers. The LRIT transponder only needs a small dish and an SDR to receive!

So here's what I did. I already had a spare 2.5 metre solid dish just laying around so put it to use for GK-2A.

Here it is here (left) next to the 2.3m dish for Himawaricast on Jcsat2B (right).
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GK-2A is located at 128.2E, a little above Asiasat 9.

So I needed to make a feed. A can feed seemed logical so after some looking around I found people making them out of old Milo tins! I just happened to have some Sustagen tins that had nice yellow caps so I used that instead.
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Inside is a quarter wave feed pin. I used a can opener to cut off the end (not shown).
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Continued...

Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 3:55 am

I mounted this inside a can pan to make a kind of choke ring. Stuffed if I know what the illumination pattern is, but it looks good!
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Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 3:57 am

Next to a C band feed.
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I bought a Nooelec SDR as this one has extended range to over 2 gHz, the cheap ebay ones are crap and don't make it to 1692 mHz.
I also bought a Nooelec Sawbird filter that has a 2 stage LNA and 80 mHz band pass filter. This gives 30dB. However I have also used
2 ebay $4 L band inline 20dB amps and they work fine too.
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My SDR waterfall display looks like this.
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Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 4:01 am

I purchased Xrit decoder from USA-Satcom for a very good price, but if you're good with Linux, Sam makes great software for GK-2A for free!
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An image comes down every 10 minutes around the clock.
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010.jpg (152.92 KiB) Viewed 1976 times

Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 4:05 am

I used an overlay map from the GK-2A internet server and overlayed it in Photoshop for country boundries
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Some stunning images of super typhoon Hagibis from GK-2A, even if it's only a single channel LRIT. This super typhoon is equivalent to a category 5 cyclone.
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Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Sun Dec 08, 2019 4:07 am

Thought I'd try an old astronomy imaging trick, where chrominance is used as an overlay to a B+W image to produce a colour image. So I found a nice map of the Earth and overlayed the colour information only. The result is a nice psuedo colour image, much like colour maps are used in Wxtoimg for NOAA satellites.

This is the end result. And that's my full disc weather satellite project using a cheap SDR.
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016.jpg (149.23 KiB) Viewed 1968 times

JEL
Posts: 149
Joined: Wed Feb 07, 2018 2:08 am

Re: Full disc weather satellite images from GK-2A

Post by JEL » Wed Jan 08, 2020 11:42 am

There is just one word: COOL! :)

So a tin-can, a short string of copper, and a sat-dish... is basically all that is required?

rtlsdrblog
Site Admin
Posts: 2506
Joined: Mon Nov 19, 2012 11:54 pm

Re: Full disc weather satellite images from GK-2A

Post by rtlsdrblog » Fri Jan 10, 2020 3:08 am

Very nice. I'll add that for GK-2A is seems that even a smallish 400x600mm grid antenna (with LNA) is enough to decode the signal.

Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Mon Jan 20, 2020 3:55 am

JEL wrote:
Wed Jan 08, 2020 11:42 am
There is just one word: COOL! :)

So a tin-can, a short string of copper, and a sat-dish... is basically all that is required?
And software, of course. I use the software from USA-Satcom but it's payware. Free software is available for Linux.

Learjet
Posts: 10
Joined: Thu Jan 24, 2019 1:17 am

Re: Full disc weather satellite images from GK-2A

Post by Learjet » Mon Jan 20, 2020 3:57 am

rtlsdrblog wrote:
Fri Jan 10, 2020 3:08 am
Very nice. I'll add that for GK-2A is seems that even a smallish 400x600mm grid antenna (with LNA) is enough to decode the signal.
Yes, many are using those small grid pack antennas. I have a long coax run so much signal gets lost in it's travel to the house.

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