Hubble side B given the go-ahead
Published on Oct 15, 2008 at 2:23 pm.
1 Comment.
Filed under space telescopes.
The Hubble Space Telescope has been largely out of commission for a couple of weeks now after a failure of its data handling unit. That has kept the HST from sending back most forms of science data. We did not lose contact with the spacecraft, so the craft was not out control or out of contact. It was able to still send back data about itself, and it could send by certain types of science data, just not the sorts of things that we’ve come to expect.
But, NASA builds things like the Hubble with a lot of redundancy. After all, this is an important piece of equipment, and if something breaks, you can’t easily fix it. Planning and sending a Space Shuttle mission to Hubble is a major undertaking. This is much more difficult than hopping on a plane and spending two weeks in some remote part of the world not serviced by regular air, land, or sea transportation, and most people don’t do that without some planning, too. And, despite being designed to be serviced in orbit, it is very difficult to work in microgravity, so astronauts need very specific training to replace and repair parts on Hubble. Furthermore, not all parts were designed to be routinely replaced. The idea behind the Space Shuttle was that it should be able to deliver payloads to orbit, and return them to Earth if needed. So, if a major failure happened, then a shuttle mission could just go get Hubble and bring it back to Earth to be repaired and returned to space in a later mission. That will now never happen. If it can’t be repaired in orbit, it will be scrapped, not returned to Earth. But, even with the option to return it for repair if needed, as envisioned at the time that the telescope was being designed, it would be best to be able to have a backup system available for critical components. The data handling unit was one of those critical components with a backup system.
But, that backup has been sitting unused for nearly 2o years. It is not clear if it will really work. And, of course, we don’t want to make matters even worse. So, engineers had to look at every possible thing that could go wrong. Could switching to the backup system somehow damage the science instruments if it were faulty? What might have gone wrong with backup just sitting there? Might the computer commands to switch to the backup somehow accidentally cause something else to happen? After all, there have been a number of software upgrades since Hubble was launched. What might have changed? Was there a chance that the backup system might have an electrical fault that would damage the entire telescope’s electrical system if the switch happened? All of these questions, and more, had to be addressed.
So, NASA was not quick to authorize a shift to use the backup until everyone was satisfied that doing so was safe and could not do even more harm. After all, even if the Hubble is inoperative now, it could still be fixed next year if the situation is not made worse. Astronomers are eager to get the Hubble back to work, but we need to be careful to do this right. Now, the word is “Go!” for the switch. If all goes well, Hubble may be able to resume normal operations in a few days. Let us hope that this goes as smoothly as is hoped.
-Astroprof
Image courtesy NASA
Dave on January 31, 2009 at 1:07 pm: 1
Thats amazing after that long of a time in space that the systems would still work as planned. Just goes to show you what fantastic engineers we are dealing with here.