From: mjessick@verizon.net   
      
   Henry Spencer wrote:   
   > In article <64c0d119.0402131731.41e49fcc@posting.google.com>,   
   > Explorer8939  wrote:   
   >   
   >>Is it possible to be in Mars orbit and collide with Olympus Mons?   
   >   
   >   
   > No, alas.  (Not that anyone would want to collide with it, but an orbit   
   > passing low over it would be quite the tourist ride...)  Aerobraking and   
   > reentry altitudes on Mars are actually similar to those on Earth -- the   
   > atmosphere is much thinner, but the weaker gravitational field means   
   > density drops off rather less rapidly with altitude.  And Olympus Mons is   
   > high, but it's not *that* high...   
      
   My remembrance of Martian aerobraking guidance studies in the late   
   1980's (single pass) was that we were using periapsis altitudes less   
   than the height of Mt. Olympus. That would depend on the mission of   
   course, and the atmospheric models have presumably been upgraded since   
   then.   
      
   - Matt   
      
   Managed to dig out a conference paper:   
   AIAA 87-2401, "Optimal Guidance for Future Space Applications,"   
   J.E.Bradt, M.V.Jessick, J.W.Hardtla. AIAA GN&C Conference 1987   
      
   The last example trajectory is a Martian aerocapture patterned   
   after the Mars Sample Return Mission studies of the day.   
   Periapsis altitude was 80000 ft, a bit less than 25km.   
   L/D 0.75 and 141 lbf/ft**2 ballistic coefficient   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)