Friday, May 08, 2009

Hubble, Here We Come

STS 125 Crew
Image Credit: NASA
If all goes on time, the space shuttle Atlantis will launch Monday at 2pm EDT on NASA's fifth and final mission to repair the Hubble Space Telescope. In the primary sign that this is a government operation, the mission is known as "Servicing Mission 4", because Servicing Mission 3 was split into two separate visits, 3A and 3B. Whatever.

Anyway, you can follow the mission many ways. In addition to traditional media, you can watch the launch and the spacewalks on NASA TV, available either from your cable/satellite provider or available streaming over the web. The mission has a page on Facebook, on MySpace, and a blog hosted by NASA. You can also follow the mission on Twitter, both through Hubble's Public Affairs Office and through the experiences of astronaut Mike Massimino, one of the mission specialists. NASA's webpage for Servicing Mission 4 contains news on the mission, as well as lots of other mission-related media and activities. And I'll do my best to keep you up to date.

Hubble itself has been trundling along for the past several months. It's not in great shape; only a couple of cameras are working, the batteries are old, and it has to send data down via a spare part. But it still has been taking some extraordinary data despite the numerous delays in the repair mission. As I mentioned last fall, these delays actually turned out to be a good thing, allowing the mission directors and astronauts to find a way to replace the broken data recorder without having to bump any other critical repairs.

During this mission, astronauts will, among other things, replace the old rechargeable batteries with new ones, replace all of Hubble's gyroscopes, fix a guidance sensor, repair some torn insulation, and install a latch so that a future rocket can grab onto Hubble and de-orbit the telescope in a controlled manner, once Hubble's life is over. The astronauts will also give Hubble two new cameras. One, the Cosmic Origins Spectrograph, will look at ultraviolet light; the other, called WFC3, is the third in a series of cameras that can take pictures in optical and infrared light. The astronauts will also attempt to repair two broken cameras, one called STIS that takes spectra of stars, and one called ACS that takes regular pictures. Both of these cameras died due to circuitry malfunctions (ACS died less than a day after we had all submitted proposals to use it during 2007!) Unlike the telescope as a whole, these cameras were not designed to be repaired, and so there are some very clever tools and techniques that had to be invented to allow the astronauts to repair the instruments.

All in all, this is a very complicated mission, and not without many risks. The astronauts are risking their lives to repair Hubble; something we astronomers are deeply grateful for and a debt we cannot repay. The repairs are all complicated. Some of them we can live without, such as if one of the cameras cannot be installed for some reason. But other repairs, such as the batteries or gyroscopes, are crucial to the well-being of the telescope. If those repairs fail, Hubble is a goner. We know that the repair team, both on the ground and in space, will do their absolute best to repair Hubble; if something doesn't work, it will not be due to a lack of training or will on the part of the repair team.

If successful, the repairs will allow Hubble to work on another several years, perhaps as many as 10 or 15 (if we get really lucky). That is fantastic for a telescope that was almost a failure due to a malformed mirror. Counting this mission and the initial launch of Hubble, our astronaut corps will have admirably serviced Hubble six times, and the data we've gotten has been worth every penny.

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