Tom Brosz wrote:
Fortunately, I think that the Mars Observer is being used to keep tabs on the atmospheric conditions, and this info is being fed back to help adjust the Odyssey course. Unlike Observer, Odyssey will not have to go in totally blind.

Alex writes:
A couple of points: (1) the operational spacecraft currently orbiting Mars is Mars Global Surveyor (MGS); Mars Observer was lost in 1993; and (2) while you correctly allude to the fact that MGS didn't have the benefit of an already-orbiting spacecraft for atmospheric density inputs, one could argue that MGS didn't really "go in totally blind." Although Mars Pathfinder expired before MGS' orbital insertion, its atmospheric measurements (both from the surface and during EDL) were fed into the MGS project and used to for aerobraking modelling. In addition, HST observations and earth-based microwave and sub-millimeter observations were used.

Alex R. Blackwell
University of Hawaii