more on Hubble Space Telescope Servicing Mission 4 and future cancelled.

[Dave Farber <dave () farber net>]

From: "Joseph C. Pistritto" <jcp () jcphome com>

Before everyone thinks this is just a reaction to the new NASA announcement 
of a couple of days ago, the Hubble mission was already in some serious 
jeopardy due to the review of Shuttle operations by the Columbia Accident 
Investigation Board (CAIB).

A number of the techniques of inspecting and repairing the Shuttle on orbit 
involve the International Space Station as a destination.   All planned 
shuttle missions *except* the single Hubble repair mission planned for 
sometime in 2006/2007 were to ISS (at least after Columbia, the only 
Shuttle that couldn't reach ISS becuase of its weight was destroyed).   Its 
fairly likely that mission was going to get canned in any event because of 
the difficulty of performing an adequate inspection on orbit at any 
location other than ISS.

Hubble's orbital inclination and ISS's are incompatable.  A Shuttle cannot 
fly from one to the other in a single mission due to orbital mechanics.

The fundamental replacable elements that will determine Hubble's lifespan 
are it's gyroscopes (which are very heavy, balky and seem to fail with 
annoying frequency, the telescope needs 3 operating ones to perform fine 
mode tracking necessary for long exposures).    These things are pretty 
big, they won't fit in a Soyuz, for instance, only Shuttle has enough cargo 
space to carry new ones.

The final word on this story may not be written yet, depending on the fate 
of the James Webb Space Telescope (Hubble's replacement which will *not* be 
at a Shuttle servicable location), I think there's a strong possibility of 
an all volunteer Shuttle mission to the telescope (while a 2nd Shuttle 
stands by on the ground), possibly at the end of Shuttle operations nearer 
2010.  However I doubt that will happen until the ISS committments have 
been met.

   -jcp- 

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