METH@USC-ISI.ARPA (10/21/85)
HST is scheduled for a 600km orbit by the shuttle. This is at the outer limits of shuttle orbital capabilities, given the payload weight. HST is designed for 5 year servicing, 20 year total life. It was originally designed for servicing on the ground at 10 years, but now with the space station, all servicing will be done on orbit. Exact maintenance and refirbishment schedule is still to be determined. HST has a significant amount of aero drag due to its large body and solar panel "wings." It will probably need a reboost every time it's serviced. On the other hand, if the orbital transfer vehicle ever becomes real, that won't be a problem (maybe it can be boosted to an even higher orbit). The aluminum coating on the mirror probably will NOT evaporate, since it's overcoated with magnesium fluoride. The REAL problem is molecular contamination, and atomic oxygen degradation. The former could be solved by burning the coating off (the Al/MgF2 won't be damamged), the latter is a relatively new phenomenon, still being quantified. --Sheldon Meth -------