Receiving images from the ISS
The ISS (International Space Station) has a radio and its crew sometimes uses to communicate with amateur radio operators and also, from time to time, to send images back to Earth!
The format they use is called SSTV (Slow Scan television), in particular its format PD120. It takes around 2 minutes to receive a full image. And you can receive this images yourself by using a small handheld radio.
How to do it
This is the image I was able to capture. Not to bad for something hundreds of kilometers away!
The downlink of the ISS is located at 145.800 MHz. I used a web to check when a pass nearby my location would happen. You are going to get a better signal if the max altitude is larger than 10°. Also, it doesn’t matter if it’s visible or not, since we are not interested in seeing it with our naked eye.
I used www.n2yo.com, but there are plenty of pages and apps with this information.
Here is an example of the path I used, from another app called SatSat:
I set the squelch of my Baofeng to 0, and then at the AOS time I started recording with my iPhone voice memos app. I had to move around to try to find the best orientation of the antenna, but eventually I found the transmission noise (you can see how it sounds and check that your SSTV decoding app works in this video).
Then I simply came back to my car, played the recording back to my MacBook runnin MultiScan 3B, and this image was decoded.
I’d say this is the bare minimum. You can also try to input the radio audio directlly into your computer, or phone, but I didn’t have the connectros needed to do this.
Transmissions will continue until Jan 1st 18:20 UTC.