Hubble Reborn:

Jeff Hoffman and Kathy Thornton

By William Harwood & Emily Baldwin

Posted: 23 December, 2009

In May 2009 Hubble received its final servicing mission that is set to see it operate well into the next decade. Five teams of astronauts have visited Hubble, and who better to tell the story of Hubble's journey than two Hubble spacewalkers, Kathy Thornton and Jeff Hoffman, both part of the team for correcting Hubble's blurry vision in the very first 'make or break' servicing mission.

Today Hubble has turned into a phenomenal success, but the telescope's faulty optics were a disaster, not just for the mission but also for NASA. What was it like being put on that mission to fix it?
JH: In order to understand what the environment was when we were preparing for the initial rescue repair mission you have to appreciate the incredible disaster that Hubble was at the time, and since it has been such an incredible success for the last 16 years since we fixed it, people have lost sight especially when I talk to students who don't even remember the problem! Hubble is such a great success now.
KT: When they did the calibration on Hubble and it turned out to be such a disaster the mission was billed as make it or break it for NASA and if we couldn't fix that we certainly couldn't build a space station, and we looked a little bit inept for launching a spacecraft of that expense and importance and not having really checked it out so it was very big deal at the time. But even with how bad it was, after mathematically deconvolving the images we were still getting amazing images of nearby objects, what was lost was the capability of looking into deep deep space but we were still getting amazing planetary pictures we had never seen before.
JH: When our crew was training up at Goddard we were invited to NASA HQ and we were told "Look guys, NASA's future for the human spaceflight program is very much in your hands because if we can't fix Hubble there is no way that congress is going to give us the go ahead to build the space station." We knew the situation. We were working as hard as we could to do everything that was possible to fix it. What did make the difference was the resources made available – all NASA's centres did what they could do to help. There was no inter-centre rivalry, everyone was pulling in the same direction: Let's rescue Hubble. That also meant we could get changes made fairly late in the mission planning that under normal circumstances would never have been considered.
KT: Some people really didn't want us to touch it – as bad as it was, you can always make it worse. Some people were afraid we were going to kill it, and we could have if for example, the solar arrays hadn't gone on, hadn't hooked up or powered up. But in every mission we do our absolute best and there was certainly a lot of additional importance in this one going off right. We focused on doing our part of it, but there were a lot of people involved in the project, and there was still the chance of the instruments not working even if we installed them perfectly.

Jeff, did you feel any extra pressure being an astronomer as well as an astronaut?
JH: In addition to the impact on NASA, I was fully aware of the impact on the astronomical community. Many astronomers were planning on making Hubble the central part of their research program so I knew very well what the impact was. I had a lot of contact with astronomers, and gave them a preview of what we were trying to do, and they would shake their heads and say "boy, you really think you can do that?" Now we take it for granted that we can do very detailed work when we're in our spacesuits, but this was an order of magnitude bigger than anything that had ever been attempted before. There was a lot of question as to whether we had bitten off more than we could chew. When we were getting ready for the first mission we were going to be handling a lot of delicate astronomical instrumentation, and they said, "are astronauts really sufficiently sensitive to how delicate these things are?" and the answer is 'yes!' – it made the astronomers feel good that an astronomer was on the mission! It's become a tradition now that on every Hubble mission there's been at least one astronomer – not that you need to be an astronomer to go up there, but it makes them feel good that at least somebody up there really appreciates the importance of Hubble.

You had a busy spacewalk schedule for that first mission, were you confident that you could get everything done?
KT: Every spacecraft we had ever touched in orbit to that point there had been a problem – it either wasn't built to the drawings we worked to or something like that. Every single one until Hubble! So I fully expected a lot more trouble than we had. I thought we were going to have trouble sticking COSTAR in – I thought we were going to get it half way in and hit something and then have to decide what to do about that. I thought we'd have an enormous amount of problems and we didn't and I think that the reason for that is the high fidelity simulator up at Goddard. The thought that went into the planning for all the servicing on Hubble is what has made all the service missions successful, and they've been more complex since then. We had planned for a lot of bad stuff to happen and fortunately none of it did, and we also concentrated on having every tool available for any task so if they pressed the airlock we were ready for anything – we had cross training enough that we could have done anything that came up on the schedule.
JT: We wondering if the normal replacement of an entire instrument was going to work well. When we were at Goddard and had the actual WFPC2 and the COSTAR installed into the big mechanical simulation, built supposedly to the same specs as the telescope itself, neither one of the instruments could be inserted the first time we tried because there were various things out of spec in the instruments on one case and on the simulation mockup in the other. But from the extensive work we had done underwater and with the real hardware at Goddard, we fully expected that if there were no unpleasant surprises we could accomplish what we had set out to do. When I got out on the first day and the doors to the gyro compartment wouldn't close, that was the sort of problem that we anticipated – had we had a few more of those problems we might have run out of time but luckily the configuration control had been very good so we pretty much found what we were expecting.

How do you think things have changed since the first and the last servicing mission?
KT: Some of the equipment has evolved based on what we have learnt, we had trouble with screws and washers floating around so later on equipment gets built that helps deal with that kind of stuff. But if you compare our service mission with the last service mission, ours in retrospect was easy, because they did open heart surgery, things that we never would have attempted on a first service mission. But as you keep going up to Hubble you get more and more confident in the instrument up there and what you can do with it and so I was amazed what they did on the last mission. As Hubble gets older I think they're willing to take more risk. I'm not sure they would have let us take out the main computer on the first mission! But as it's gotten older in its life cycle you're willing to take on a little more risk to improve it, and particularly as you see the end of the shuttle program winding down it's our last chance to visit Hubble with people, so you really want to take some risks in order to extend the lifetime as far into the future as you can.
JH: If someone had suggested we open up an instrument and take out the electronic boards at that time in the experience, that wouldn't have been the right decision - you don't take a leap quite that far, in addition to the fact at the time there was no need to do it. The STS-125 crew fully expected to be able to complete the mission, barring unexpected difficulties. The big difference between the first and subsequent missions was that when we were going up there were a great may people who doubted that the whole mission could be accomplished – sure we would get some of it done but not all of it, it was too ambitious – whereas now we go into these missions with everyone thinking its going to be 100 percent successful. That's the price you pay for success! But it doesn't mean people have let their guard down or worked any less hard at preparing for it, that's why the missions continue to be successful, it's hard work preparing for these missions, and the amount of time you spend training underwater is every bit as great.
I trained with the second mission to give advice. Unfortunately after the first mission the office management decided that Hubble is such a good deal you don't get to do it again but when the second crew had a big surprise in realising the thermal insulation was peeling off that shock people up in management and they realised that Hubble really is a serious undertaking and they needed to bring expertise from one flight to another. They want people who have worked on Hubble to develop the new procedures. After the first mission and before they assigned a crew for the second, I was basically working with the Hubble people in the water tank developing future procedures. On the third mission where they replaced the power control unit that was a huge challenge with all those connectors so I helped develop the procedure for doing that. It helps when you've been up there, you have a feeling for it, you know what works and not, it makes it work.

What were some of the challenges you faced during STS-61?
KT: In the first spacewalk we changed out the solar arrays. We knew before we went out the door that one of them was not going to roll up, so that was going to be a jettison, which we trained for, which was really neat. It was so easy to handle, you could move it with your fingertips. I was supposed to put on some thermal gloves as it wasn't clear how long I'd be there hanging out on the end of the arm holding this thing before sunrise when we could jettison it. That was probably the hardest thing trying to get these thermal gloves on top of my EVA gloves, but I could sort of let go of the solar arrays and let it float in front of my face while I put my gloves on, and I would check it every now and then to put it back where I wanted it, but it was really easy to handle. And when it came to the jettison I just took my hands away. When we did the separation maneuver the jet plumes hit the solar arrays and caused it to almost bend over double, and then it just sprung back out tumbling and cruising over the desert and it made me realise these things are a lot sturdier than everybody gave them credit for – there was lots of concern as to how unstable it would be, particularly for the next service mission they were concerned that just shaking the telescope could cause this thing to roll up, but I just got the impression that in orbit when it's supporting its weight they are a lot studier and robust we gave them credit for. <br> Another problem was that my communications didn't work, I couldn't hear anyone except Tom! Flight rules said I could go as long as I could hear somebody, so for most of the two EVAs I could only hear Tom. For me it was really great – I didn't hear any static, I didn't hear the chatter from the ground to the orbiter or back. The only problem was I didn't talk very much because I couldn't tell if I was talking over somebody, so I kept pretty quiet.
We also had a little trouble getting the doors closed after the COSTAR instrument installation and we knew as soon as we opened the handle to open the door. I saw one of them sag – there was some stored energy in there and then as we pulled it open we could see scuff marks at the bottom so it was clear that in orbit testing they were having to lift it in order to close this door.

What are your most enduring memories from the mission?
KT: There was one time when I was on the arm and I was being moved from one position to another which is pretty slow and I wasn't really paying any attention at all to where I was, then I looked up and we were over the Gulf of Mexico and I could see the entire outline of North America and even some aurora up over Canada. I could look one way and see the west coast and turn the other to the east coast, it was an amazing sight so we hung there for a little bit, but we don't spend a lot of time sightseeing up there.
JH: The first view of Hubble is always a thrill, although the first mission was tempered by the sorry state of the solar arrays that we had to leave in space. The first time I touched the telescope was a big thrill, for an astronomer and an astronaut to touch Hubble. Another high point was when the WFPC went in and we closed it up and I knew the optical problem was at least partially fixed. An astronomer friend called me shortly before the mission went and said, "Jeff, we realise that the chance of completing everything is small because it is so complicated but we just want to let you know that if you can get either the WFPC or the COSTAR installed, here at the institute we'll be overjoyed, and we will consider the mission a success." When the WFPC went in I felt good, and after the fifth EVA everything that had been put on our plate we had accomplished, so that was a very good feeling.

What was your reaction to the mission being such a success?
KT: It was great that it worked out, but we didn't know it was going to work out when we landed until they calibrated it and started getting pictures back. It didn't matter that we had done everything we could do if Hubble didn't work it was a failure. But then we heard that everything looked really good. The pictures are just gorgeous, I have some here on my walls that I just stare at, they're unbelievable. The Pillars of Creation, the Eagle Nebula, that was one of the first, and that's my picture of heaven.
JH: We knew of course that everything we had done was successful but whether the optics were really correct we wouldn't know until they turned on the instruments a couple of weeks later. I got a call on New Year's Eve from a friend at the institute at like 1.30 in the morning while I was cleaning up after a party. He said "you got any champagne leftover? Really no one is supposed to know this yet because there will be a public announcement, but we figured we had to let somebody on the crew know that we had got the first pictures back from Hubble and it works." Boy was that a thrill, and I did drink some champagne!

Did you imagine, at that point in 1993, that Hubble would still be going in 2009?
KT: Not when the RGAs were dying at such a prodigious rate and the telescope went into safe mode a couple of times. It was pretty dicy at times when they had to bring up an emergency mission. You had to wonder problematically whether NASA was willing to put on an additional servicing mission at the cost of whatever it cost, but it's amazing it's still going. It gets better each time, things don't normally work like that. I still feel like I'm a part of it. Hubble is the big one, I was lucky to be on it.
JH: That was the plan! Particularly once we demonstrated that the servicing really worked, that we could take these instruments out and replace them with new instruments, and repair electronic parts. We didn't anticipate changing out electronic boards like on this past mission, but every time we went up to Hubble we gained confidence in what we could do and so we attempted more than we had on the last mission.

You could build a lot of ground-based telescopes for the cost of a space-based telescope like Hubble, is it worth it?
JH: The ground-based telescopes are getting more expensive too, but you are always gaining something by going into space. These large ground-based telescopes are superb once you've discovered something interesting you can zero in and with a great collecting power you can do a great job with spectroscopy, but they're not nearly as good for discovery as Hubble or other space telescopes. What we basically did with Hubble was to take the culmination of telescope technology of the mid-twentieth century like Palomar – a big mirror single monolithic – and we put it in space. Now with JWST we're taking the multi-mirror type of technology and infrared technology that has been developed in the latter part of the twentieth century and we're going to put that into space, and I think that's the right way to go about space astronomy. We develop these new optical technologies on the ground and then eventually you get the best of what's available and you put into space. You won't do it nearly as frequently as you build ground telescopes because it is so expensive but there's no way that we would have accomplished with just ground-based telescopes what Hubble has over these last 15 years.
We don't do it for its economical benefits, it's a cultural activity and how do we put a price on that? It's changed the way humans look at the Universe and the public seems to love Hubble. More people know about Hubble than any other telescope in the world and they love it. When [former NASA Administrator] Sean O'Keefe tried to cancel the final servicing mission the response from the public was apparently stronger than the response from the astronomy community so there's no way specifically to answer whether it's worth X billion dollars because we don't put that sort of a value on astronomy. On the other hand, take the discovery of dark energy and the whole acceleration of the Universe – what that's told us is that our physics is totally incomplete and so ultimately that may lead to a break-through in physics. It's like at the end of the 19th century people thought we knew all that there was about physics and then along came quantum mechanics and relativity – look at the economic benefit that came out of that – so who knows what will come out of the next major advance in physics that will explain these new things. These things tend to pay for themselves.

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