They most have built a ton of backup functions in it. Amazing, thats what it is.

I was watching a program about the Galileo spacecraft the other day. The high gain antenna didn't deploy properly and since the time it was launched, they had developed new technology to repair some of the problems. They were able to beam new instructions to Galileo and were still able to get tons of useful data so the program wasn't a total loss. It's pretty amazing what they can do from millions of miles away...