[Chingers]

There is a company that already does this, they use it to track ships that turn off their transponders or AIS systems. I think it was shared on hn recently, but I can't find the article anymore

[Sayrus]

I think that's the one: https://jackpoulson.substack.com/p/lockheed-is-now-tracking-...

[perihelions]

Oh yeah, I saw that one too! Don't remember what tech they were using.