Well, I'd like to... What would it take to space harden an AVR? Or do space hardened AVRs exist already?
If I had to use a PIC or some other microcontroller I would, but I don't think there are any space hardened PICs either.
Basically the main things it would have to deal with, as far as I can tell, is a massive amount of radiation and lack of convection for cooling.
The cooling would be simple enough, just attach every single thing to a heatsink (probably including passive devices like resistors and capacitors). Another cooling idea I had was, if it didn't add too much weight, some kind of fluid cooling. The problem there, of course, is freezing (space is a place of extremes, the melting and boiling temperature of things tend to be very close together in such an environment).
The radiation is much harder to deal with. Some could be minimized by putting the major electronics in a Faraday cage. However that wouldn't stop everything. A magnetic field would work but would probably be too electrically expensive. Embedding it in three feet of lead would also work but that would be too heavy to get into orbit.
What I want is to be able to build a cheap robot with a camera that could go to the Moon or Mars and wander around taking pictures, the Moon would be preferable. My dinky little webcam that I got for $12 has far better picture quality than the expensive cameras they brought with them during Apollo. There hasn't been a single picture taken from the surface of the moon in almost 40 years.
My conclusion so far has been that the reason space-based robots tend to be extremely expensive (in the range of billions of dollars) has less to do with what they make them out of than how much it costs to get there. In other words if it costs on the order of trillions to get there then it doesn't really matter if you're spending $1000 on your robot or $10 billion, it's such a tiny part of the overall cost anyway, might as well make it worth it.
My approach is to figure out if it's even possible for me to build a robot that will work there, then figure out the cheapest way to get it there.
I know people have put Arduinos on high altitude balloons, but they're still in the Earth's magnetosphere (unless they were near the poles) and so wouldn't have to deal with radiation as much.