Tuesday, September 30, 2008

Hubble's problem is more like a flat tire than a wreck

A mechanic fixes a flat tire
An astronaut repairs Hubble's broken Side A Data Science Formatter
Image Credit: North Carolina Department of Transportation

My blood pressure went up today when I read headlines saying "Hubble telescope fails" or "Is the Broken Hubble Telescope Worth Saving?" These headlines make it sounds like a horrible calamity has befallen Hubble.

As I said yesterday, Hubble is not dead. Having a problem, yes, but far from "failed" or beyond repair. All that has happened is that Hubble has lost a part necessary for sending its scientific data (pictures) back to Earth. There is a backup that scientists are booting up (this takes a few weeks), and the whole unit (main plus backup) can probably be replaced in a couple of hours by the astronauts when the next Hubble repair mission goes.

I think a good analogy involves car trouble. Suppose you are driving across the west Texas desert, you're about 10 miles from an exit, and you get a flat tire. You have to stop the car, get out the spare, and put the spare on the car. Then you drive to the exit, go to a repair shop, and get the flat patched. Now, you have four good tires, still have a spare, and you're safe to hit the road (which is good, because it's 100 miles to the next town). This is the situation we think Hubble is in. It can't do science right now until the spare electronics are going, but once they are up, Hubble will be good to go until the repair mission shows up in a few months. After that, the broken unit will be replaced, and Hubble will be good to go for another 5-15 years.

Now, suppose you're in the car with a flat tire, and you find that you forgot to keep your spare inflated, so it's flat, too. What happens? You get a little angry, call AAA, and wait for the tow truck, which takes you to the exit, where you get the tire fixed and the spare inflated, and then you're good to go. Yes, you lost some time waiting for the tow truck, but otherwise you're no worse for the wear. If Hubble's spare data electronics package doesn't work, this is the situation Hubble will be in. It will have to wait for the repair mission before it can take data again, but we still think that the repairs would fix everything, and Hubble is again good to go for 5-15 years.

Now suppose you are driving, and you don't have a flat at the exit, so you fill up with gas in the town and start down the road again. Suddenly, 100 miles from anywhere, you get a flat. Now you are in trouble. If your spare is inflated, you can keep going, but you're down to no spare tire. And, if your spare is deflated, you are in serious trouble. That's the situation we would have been in if Hubble's electronics had continued to work until just after the repair mission. Thankfully we aren't there!

Now, think of worst-case scenarios. You're driving across west Texas and have a wreck, or the transmission falls out of the car, or the car catches fire. That's bad. Your car is toast, and now only worth the value of the scrap metal, which isn't much. Hubble is not in this situation. Like a car with a flat tire, Hubble can't operate properly, but it isn't a worthless hunk of scrap metal.

So, I think it completely overstates the problem to say that Hubble has failed, and it gives people the impression that the telescope is just a pile of scrap metal. As I said, that's not the right impression. Part of Hubble, a repairable part that has a spare already on board, quite working. But we think the spare will work. And, if the spare doesn't work, the space shuttle is coming to the rescue soon. We just need to (a) figure out what happened, and (b) train the astronauts how to fix it. Worst case scenario: we have to wait three months for any more pretty pictures from Hubble. And, while it may be annoying, it's no worse than waiting for that tow truck. At least we know it's not far away and it's coming, and we'll all be back in business soon.

1 comment:

  1. Brilliant explanation. We'll be posting it to the AAVSO Writers Bureau to make sure that your well reasoned explanation gets out to the general astronomy public.
    Keep up the good work.

    Mike Simonsen