P2K: Just how different is the Mars Exploration Rovers mission to Pathfinder?

Rob Manning: I think the biggest difference is that we have an expectation of success that Pathfinder did not have. Pathfinder, in some sense, you can get a lot of mileage out of the fact that people think it's not going to work! You can take the risks... the risks are yourself... personal. If Pathfinder did not work, I would be the one who was disappointed. The outside world would have had their expectations been met. This project, the Mars Exploration Rovers mission... we are... this is... a science mission. We are trying to do science on Mars. The objective is not to land safely. The objective is to land safely and do a lot of very interesting science. And that's very laudable. And for the money we spend, it's the right thing to do.

However the expectation value of our mission has gone way up. And with that we need to spend all that much more time thinking and try to parse out the subtlety, the little details, to really understand "Why is this number the way it is, why can't it be higher, why can't it be lower." And that is something we do... it costs more time, more money, and more engineering time to think through those details that we never had time, or the money to think about on Pathfinder. In fact problems we did not even know existed that were on Pathfinder, that have now been uncovered on this project are now taking all of our attention to really understand.