Servicing Mission 4: What's Next for Hubble?

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Q & A

with Dr. Keith Noll

Dr. Keith Noll

In September 2009, the first post-Servicing Mission 4 images from the Hubble Space Telescope were released. These Early Release Observations (EROs) gave the world the first glimpse of the capabilities of the upgraded and restored telescope. Dr. Keith Noll, astronomer at the Space Telescope Science Institute, led the Early Release Observation team, which selected the targets and planned the observations.

Tell me about your involvement with the Early Release Observations.

I'm the ERO lead, and that means that I'm sort of in charge of the process. It's a very complicated process and there are a lot of people who have contributed to this. A lot of what I do is coordinating the work that other people have been doing.

What are the Early Release Observations?

Every time we have a servicing mission, something has been done to the telescope. This time we've installed two new instruments and repaired two. So naturally people are anxious to see how they work. The Early Release Observations are the first full observations that get done that are intended for release to the public and intended to show what the new instruments can do.

Why is there such a stretch of time between the mission and the EROs?

Turning on an instrument is a very painstaking process because we have this very expensive new thing up there, and we do it in tiny, tiny baby steps. So it takes awhile. Even though the astronauts put the instruments in in May, we won't get the early release data until quite a bit later in the summer.

Does Hubble take any images before the EROs?

We will be getting some things back from the spacecraft, but they're more of the engineering variety. If you want to show people, you wouldn't really be able to show them those images, because they would require a lot of explanation. The EROs are the first really nice images and spectra.

Is there any scientific value to the EROs?

Well, like all the images we do for outreach, they can be and are used for science. And we always make sure we do them in a way that preserves the value for scientific applications. As soon as the data are released, they're available to any researcher through our archives. In the past, these kinds of images have been used for science and we expect that will be true this time as well.

How do you go about deciding what these images will be?

We've been at this for about two years. In the beginning we had teleconferences and meetings that involved representatives from each of the two new instruments, the two instruments that would be repaired, the Institute, the news team, and representatives from Goddard and NASA headquarters. So a lot of people were involved in this.

In the beginning, we brainstorm and come up with lots and lots and lots of ideas. Then we go through a process of talking through each one, weighing the advantages and disadvantages, and start narrowing down until we got to a list we felt was really a good mix and had other good properties.

What kinds of properties?

Technical things like targets with wide visibility windows — because we didn't know exactly when servicing mission was going to take place, so we biased our targets towards ones with long visibilities. Which helped because we did have launch delays. Time constraints — we want it to be impressive and spectacular, but there are limits to how much time we can spend on it, since scientists are anxious to start using the observatory to do their science. That's one of the compromises: big, bold, spectacular versus how much time we want to spend on it. We also want a good mix of astronomical objects — galactic and extragalactic, near and far, different kinds of targets. I think we also did that — pick a good mix. And we wanted to pick targets that show off the new capabilities the new instruments bring.

Is it normal for it to be a two-year process?

No, that was unusual this time because of the delays. But a year is normal. The amount of planning that goes into a servicing mission — not just the EROs but the whole mission, is probably hard for people outside this activity to imagine. It's literally years of planning that goes into a successful servicing mission and the work of thousands of people.

What takes so long to make the choices — is it the amount of choices, or is there a lot of debate?

We would have a lot of debate about them. Because the process involves so many people, it takes time. We could probably design a more efficient process — have one person go and select their favorite targets and be done, but by going through the process it was clear to me we ended up with a much better list than any one person could have ended up with on their own. My idea of what were the best targets really changed as we went through the process.

Are people really passionate about their choices?

(Laughs) At times, yes — we had some spirited debates. But everyone had the same goal in mind: How do we get the message out that we have a brand new telescope and show off some of the new capabilities. The new cameras have some amazing capabilities we never had before, to go into the ultraviolet and infrared — very specific wavelengths of light where we have emission lines for different atoms of interest, and we wanted to show that off. Some of that is more for the more — how should I say it — geeky community, including scientists. And that plays into why it's so complicated — you want a target for a wide range of interests, from casual to our scientific colleagues.

What sort of capabilities will people see when they look at the new images from Wide Field Camera 3?

Wide Field Camera 3 has an incredible array of filters, much more than any of our previous cameras, and it's much more sensitive at shorter wavelengths — the blue and into the ultraviolet and in the infrared. So we've selected things that show that off. It may not be obvious to the casual observer but if you dig a little bit into it, I think it'll be pretty clear what the new capabilities are.

How about the Cosmic Origins Spectrograph (COS)?

That's one you need a little more knowledge to understand because it's a spectrograph and that requires a little more familiarity with what we're doing. It's much more sensitive than the previous spectrograph. So it'll be able to do things we could barely do or not do at all. It's a little more technical but we'll be able to show that off with the targets we've selected.

What should they expect to see from COS?

It doesn't take images on its own. We are going to take images of some of the targets being observed by COS, so people will be able to see a Hubble image of the COS target. But the COS data itself is a spectrum — what they'll see is a graph with curvy lines on it. If you're trained, those curvy lines contain a fantastic wealth of detail — like looking at fingerprints, essentially. They can tell you the composition of the gas, the temperature of the gas, the ionization state of the gas — and all these things are tremendous clues to what's going on in the different targets.

Are there also going to be images from the fixed instruments?

Yes we'll have EROs from the Advanced Cameras for Surveys and (the Space Telescope Imaging Spectrograph) STIS, which is our previous spectrograph.

So what will the ERO targets be?

The tradition has been to keep the identities secret until the time when they're released, and there are a couple of reasons. One is that it's more fun that way — there's no fun in knowing a surprise in advance. The other is that we hope every one of these will be perfect, but we can't be sure. If something goes wrong, we don't want to have promised something we can't deliver.

How impressive will it be looking at the new images compared to what people are used to seeing from Hubble?

The bar has been raised quite a bit over the lifetime of Hubble. If you look back at some of the older EROs, they wouldn't be impressive now. At the time they really were, but we've continually gotten better with the capabilities of the telescope. So it gets harder and harder to top what we've done before. I think they're going to be very impressive, but we've done so many impressive things already it may not be that much of a leap. But after spending the last year or so limping along on reduced capabilities, with the aging camera, and the other camera not functioning, and the spectrograph not functioning, what's really going to be exciting is seeing a fully functioning observatory that has all its instruments going. It'll be really exciting to see that back.

Are the EROs a big deal in the astronomy community?

I think so. Even when you kind of know the technical details, I think for all of us there's still kind of the wonder that you have as a kid, seeing something and saying "Wow." That's a nice experience, a nice validation of all the work you've been doing.

What are you most excited about seeing, personally?

I'm excited to see if they all work, because after putting this much effort into it, I'm a nervous parent at this point, waiting to see everything come through and be okay. I think they're all going to be great — I don't have a favorite at this point.

Spoken like a true parent.

That's right.