[X] My Assistant

[Phil Stooke]

I like asking questions, and where better than a place like this?

So here's one... Mars Climate Orbiter burned up during a too-low pass through the atmosphere. So where would its debris have fallen?

This ought to be a fairly straightforward question to answer. We presumably know, or can find, the details of its trajectory as it approached Mars. We know the orientation of Mars at the time. The location of periapsis in Mars coordinates ought to be easy to find. This might be buried in a technical report somewhere, or it might be possible to figure it out with one of the solar system simulator type programs. Can anybody help answer this?

(if so, we can extend it to Pioneer Venus and Magellan later in a separate thread)

Phil

[Guest_BruceMoomaw_*]

If I may provide yet another advance ad for my "Astronomy" article: those upward and downward jumps in Martian upper-atmosphere density have turned out to be so big, hard to predict, and dangerous for landers (and maybe for aerocaptured craft) that their study is turning into a major theme in the near-future Mars program -- as an engineering necessity.

[mcaplinger]

...those upward and downward jumps in Martian upper-atmosphere density have turned out to be so big, hard to predict, and dangerous for landers (and maybe for aerocaptured craft) that their study is turning into a major theme in the near-future Mars program -- as an engineering necessity.

Maybe instead we should use entry systems with more margin against these sorts of problems. I don't know how much of what Bruce is saying about Spirit is reality and how much engineering conservatism, but it's always been understood that MER had fairly poor robustness in the face of some environmental factors. There are two engineering responses to this: ask "the scientists" for better environmental data, or design proper margins into the system based on the uncertainties (probably losing capability in the bargain.) One is looking for the proper mix, but it's likely not on one end or the other of this spectrum.