I don't know much personally about SAR applications. But in terms of the projects I've done, the temperature and size of the target is fairly predictable compared to noise in the image. While it's not as easy as "filter anything above this temperature as a positive", it's an easier engineering program than 3D navigation.

> I'd love to hear more about cases in which IR has made a difference in a search, because that hasn't been my experience or what I've heard about it.

Here's another link where IR was used to find seven missing people, same trial program: https://bc.ctvnews.ca/a-b-c-first-heat-seeking-drone-used-in...

While looking more into this though, they mentioned that one of the things the program found is that the drones are not good at seeing through tree canopies. This is surprising for me, and I suppose answers my question about why this MIT project has some benefit! I stand corrected in that regard.

> There are some environments where IR might help, but many more where it doesn't.

Absolutely. There's no magic solution for finding people. The project here is going to have pros and cons too, you need experienced people to know what tool makes sense where.