Cubesats Are Fascinating Learning Tools for Space

Yes, a Raspberry Pi isn't radiation hardened, but in LEO (say around 400-500 km) the radiation environment isn't that severe. Total ionizing dose is not a problem. High energy particles causing single event effects are an issue, but these can be addressed with design mitigations: a window watchdog timer to reset the Pi, multiple copies of flight software on different flash ICs to switch between if one copy is corrupted, latchup detection circuits, etc. None of these mitigations require expensive space qualified hardware to reasonably address.

The usual issues I see in academic CubeSats are mostly programmatic. These things are usually built by students, and generally speaking a CubeSat project is just a bit too long (3-4 years design and build + 1-2 years operations) to have good continuity of personnel, you usually have nobody left at the end there since the beginning except the principal investigator and maybe a couple PhD students.

And since everyone is very green (for many students, this is their first serious multidisciplinary development effort) people are bound to make mistakes. Now, that's a good thing, the whole point is learning. The problem is that extensive testing is usually neglected on academic CubeSats, either because of time pressure to meet a launch date or the team simply doesn't know how to test effectively. So, they'll launch it, and it'll be DOA on orbit since nobody did a fully integrated test campaign.

inquiring minds want to know. was this tethered? what kind of clearance did you need and what kind of equipment was necessary for safety purposes?

https://github.com/nasa-jpl/open-source-rover

It is somewhat different from a security point of view, but the gap between them is getting smaller. The main "obstacle" to hackers taking over your satellite is that it is somewhat difficult to set up a UHF/VHF/S-band ground station with enough transmit power to reach the satellite. And you need knowledge of the command protocol that the satellite uses. But ground stations are getting cheaper every day, IMO you can build a fairly capable transmitting setup for ~1000€. So the remaining protection is a form of security by obscurity: "we invented this command protocol, so nobody knows how it works". But that can obviously be defeated by recording ground station signals and some dedicated reverse engineers.

When those protections fall away, you'll find that a lot of satellite/CubeSat software out there is quite vulnerable (see https://jwillbold.com/paper/willbold2023spaceodyssey.pdf). You often find things like commands that are literally "arbitrary memory read/write". While they are a nightmare from a security point of view, they are extremely useful for operators of experimental satellites, e.g. to patch software in memory to fix bugs or read variables that are not exposed as telemetry. I have written a few of these patches myself, and my friend PistonMiner used them brilliantly to hack in a software update capability and revived a 15 year old CubeSat that was assumed to be dead - see their 38C3 talk: https://www.youtube.com/watch?v=KdTcd94pVlY

If you ask me, the way to keep satellites secure is to basically apply the lessons that we have learned in terrestrial computing to space applications. Things like using encryption/authentication, process isolation backed by a MMU, memory safe languages, etc. That's what we're trying to do with RACCOON OS btw. You can take at the flight software of CyBEEsat, a 1U CubeSat that is launching soon(tm): https://gitlab.com/rccn/missions/cybeesat

On the satellite it’s just an off the shelf UHF/VHF transmitter or SDR.

Not really. They typically use standard amatuer radio frequencies and protocols. Making space to ground contacts is doable with a handheld radio and directional antenna. Main limitation is low data rates (dialup or worse) and low coverage (you'll probably only get 1-2 passes a day from a single ground station). A decent semi-permament ground station can be built from off the shelf parts at a fraction of the cost of the overall satellite.