My co-workers and I just watched the presentation at Goddard (we got a remote feed into our auditorium) where NASA Administrator Michael Griffin announced that he’d given SM4 (actually the fifth servicing mission) to the Hubble Space Telescope the go-ahead. 

The main points were that: the shuttle engineers and astronauts had demonstrated they had a workable means of repairing the most likely sorts of damage to the shuttle in-flight, and a second shuttle would be waiting on the launch pad in case it was needed to rescue the first shuttle crew.  That last scenario seems at this point to be a remote need, since the kind of damage that caused the breakup on reentry of Columbia can now it seems, be repaired in space.  But the added safety factor still makes having that second shuttle ready worthwhile.

So (whew!) we’re good to go.  And if the mission is successful, Hubble should be generating good science up to 2013.