Another thing about this is that how much compute power do these things actually NEED? These things need to move slow for reliability reasons ANYWAY and transmitting the type of data these things are going to collect doesn't take that much power. It already sent 1080p video back so how much more power do we actually need? I'm sure the minds at NASA would be great at optimizing code instead of programs today that rely on raw horsepower. Why spend resources optimizing code when you can count on a 50-70% increase in hardware performance every year?
Optimizing code goes a LONG way but is expensive to do. In something like this where money is essentially no object the budget is there to optimize the code