The just landed 'Perseverance' Mars rover's helicopter, 'Ingenuity, is built on Linux and JPL's open source F' framework. It's mentioned at the end of IEEE Spectrum's article about the latest Mars landing.

"Anything else you can share with us that engineers might find particularly interesting?

"This the first time we’ll be flying Linux on Mars. We’re actually running on a Linux operating system. The software framework that we’re using is one that we developed at JPL for cubesats and instruments, and we open-sourced it a few years ago. So, you can get the software framework that’s flying on the Mars helicopter, and use it on your own project. It’s kind of an open-source victory, because we’re flying an open-source operating system and an open-source flight software framework and flying commercial parts that you can buy off the shelf if you wanted to do this yourself someday. This is a new thing for JPL because they tend to like what’s very safe and proven, but a lot of people are very excited about it, and we’re really looking forward to doing it."

JPL's F' framework OS is available for download on GitHub: https://github.com/nasa/fprime