Why? I doubt that Linux controls everything. I imagine it's used for the core higher level functions of the satellites themselves, but I'm sure processes runnin

Why? I doubt that Linux controls everything. I imagine it's used for the core higher level functions of the satellites themselves, but I'm sure processes running in Linux will eventually comms with lower level hardware that is indeed running an rtos or similar. In the same way that any pi project should really use i2c or spi to comms with hardware that's more purpose designed.