The hell are those guys doing? I always had the itch, but never pulled the trigger on getting my feet wet into SDR. Radio astronomy?

It's a ham radio contest station. Doesn't really have to do with SDR.

https://www.youtube.com/watch?v=Dd4NWyFq-dM

Tim’s station is one of the biggest in the world. His tallest tower is 240 feet high.

Some stations do use SDRs to feed the reverse beacon site. https://beta.reversebeacon.net/main.php