What about the other new instrument?
The Cosmic Origins Spectrograph (COS) is the other box, as it were, and it has its own two channels. It's a spectrograph, not a camera, so it takes the light from a distant light source and spreads it out into its component colors. If you measure how the intensity of light changes as a function of color, that gives you a lot of information about the medium that emitted that light—its temperature, density, rotation, chemical composition, and so on.
This is the most sensitive spectrograph ever to fly in space, to the best of our knowledge. And the combination of the spectrograph behind our telescope will allow the observers to look at very distant light sources, such as quasars, and use them as background flashlight beams. A beam of light from a distant quasar will pass through the material between the galaxies, and that material is dark—it's not what we call dark matter, but it's not glowing, it doesn't emit its own light. So you have to look at the imprint of absorption that it leaves on light passing through it. And the idea in doing this is to analyze what's called the cosmic web—the large-scale, weblike structure within which galaxies are formed.
I like to say we're going to trace the story of galaxy formation and evolution from the nursery to advanced adulthood. And COS will play a huge role in that, complementing the Wide Field Camera 3 in the process—the two instruments can work together to put together this family album of galaxy history.
As you mentioned before, this is Hubble's last servicing mission. It appears that the shuttle program is now truly entering its planned obsolescence. Is there some chance that, if Hubble manages to hang on and NASA readies a replacement spaceflight system in time, there could be another mission to Hubble?
That is principally a policy question: Do you spend more money servicing Hubble, which will be 25 years old at the end of the life extension that we're trying to achieve here?
So the planned life extension from this mission is to get it to at least 2014 or so?
That's right. And of course it's going to be a remarkably refurbished observatory with lots of new things on board, so it wouldn't surprise anyone if it kept going much longer than that, but on paper that's the objective.
So now you have an observatory that may be working fine and that has upgraded technology on it, but it's 24 or 25 years old and is a rather small telescope in space. Would you rather spend money continuing its lifetime for another five or 10 years, or would you rather invest that money in building a similar telescope that is much bigger?
There are two camps: One camp says it's going to be a long time before we get the next big telescope after Hubble and the [infrared-only] James Webb Space Telescope, and we'll need…[Hubble's]…ultraviolet, visible and near-infrared capability. So in the interim, "Let's go ahead and plan another servicing mission using the Constellation vehicles that are being developed to replace the shuttle." The other school of thought says, "Let's use that money to go for the next big step." And right now the latter is the official policy of NASA.
I really do think we need to get on with what I like to call Daughter of Hubble, with an aperture of between nine and 16 meters, rather than Hubble's 2.4 meters. I can hardly imagine what we would see with that.