[IP] more on Hubble Space Telescope Servicing Mission 4 and future cancelled.
From: "Joseph C. Pistritto" <jcp@xxxxxxxxxxx>
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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