It looks like we're going to get a decision soon on whether or not NASA is going to service the Hubble Space Telescope. Here's the deal: Hubble is designed to undergo periodic upgrades. Designers knew that technology would advance, and astronomical detectors would get better with time. So they built Hubble in a way that allowed astronauts to go there and pull out old stuff and out in the new. For example, there was one camera on board Hubble called STIS. It went up in 1997 to replace an older spectrograph. In all, there have been four servicing missions so far (NASA doesn't like to call them repair missions, and honestly, they aren't fixing it, they're updating it).
But there's more to it. There are gyroscopes on Hubble that keep it stable and locked on its targets. They're similar to toy gyroscopes, but a lot bigger and substantially more expensive. Since they spin rapidly, they wear out quickly. Hubble normally runs on three, and can do OK on two (it usually has six: three are backups). Two are not functioning any more, and it's only using two now; two functioning gyros were shut off to preserve them. The gyros can be replaced as well, and they have been in the past.
The problem as it stands now is that the remaining ones are getting old (they were installed in December 1999). If it has to, Hubble can limp by on one gyro, but if that last one fails, Hubble will start to tumble. That's a disaster: if that happens no rocket can dock to it to fix it! So time is important. If we're gonna fix it, it needs to be done soon.
So NASA is pondering this right now. There are issues: the Shuttle is due for retirement in 2010, and there is only so much time to get the space station completed. Squeezing Hubble in may be a problem, especially since NASA lost quite a bit of time with the destruction of Columbia. Safety is a concern: it was mandated that the Shuttle needs to be able to reach the station if anything goes wrong, and it's on a very different orbit than Hubble. The Shuttle can't go to Hubble and the station. So the rules will have to be bent.
But I'm confident NASA will choose to go upgrade Hubble. Why? Well, for one, they recently relaxed the restriction that all launches be during the day (for safety reasons). That makes it easier to get to Hubble, and implies NASA is willing to take some small risks. Also, Mike Griffin, the NASA Administrator, has said that Hubble is a priority.
We'll see soon enough. Engineers are scheduled to meet Friday, and rumor has it that an announcement may be made by Tuesday. I'll have more info posted here when I find it out!
Finally, I'll admit to a personal stake in this. I worked on STIS for many years, before it was launched. After many years of service, it shorted out in August 2004 and could no longer be used. If this servicing mission gets the go-ahead, there are plans to replace the dead parts on STIS, and it'll be up and running again. I'd like to see that. Plus, two more great cameras will be put on board, and the boost to space science will be fantastic. It would be truly fantastic to see the grand old lady of space observatories back up to speed.