The James Webb Space Telescope: a 12 year retrospective

Bringing back a blast from the past
17 October 2023

Interview with 

Matt Mountain, Association of Universities for Research in Astronomy




Before we can look at how this telescope is unlocking the history of the universe, we must first look at the history of the telescope itself. And what better way to do so than with a very special retrospective. In 2011, Dr Matt Mountain, the then director of the Space Telescope Science Institute, came onto the Naked Scientists to talk about overseeing some of the development of the James Webb Space Telescope. Many hopeful predictions around timeframe and budget were made, so how well did they stack up? Well, Matt is now President of the Association of Universities for Research in Astronomy, and looks back at The JWSTs development.

Will - Matt, thank you very much for coming back to speak with us. Let's start with the cost in 2011. You were very honest and upfront about saying that the price tag had gone up from an estimated $4.5 billion to $9.3 billion. Did that then keep on budget?

Matt - <laugh> No. Um, <laugh> like all of these things, when you do one-offs, every time you think it's safe to go out, you discover something else. So one of the problems when you build this very complicated space telescope is right. We make these incredibly lightweight, high precision optics that have to unfold a million miles from Earth, and then you have to fold it up and you have to have this sun shade wrapped around it. You know, it's the size of a tennis court, but think of a tennis court made of five layers of space blanket. So you have to carefully fold up this space blanket not to rip it, and you pack all this in. The real problem is you then have to put it on top of a rocket, and rockets are really violent things. They shake and they have lots of sound.

Matt - And so to make sure the thing doesn't fall apart doing this, you test it, you put all this stuff together, and we have these big shakers. Northrop Grumman has one, NASA has one, and you shake the whole of this beautiful optical system and there's lightweight sunshade and all the instruments, you shake the bejeebus out of it as though it was being launched. Unfortunately, during one of those shake tests, a dozen or so small nuts fell onto the floor in the shake room. And it turns out that in fact all of the hundreds of these small little bolts and nuts had not been installed properly and all had to be replaced. And that put at least a year and a half delay and cost us an extra $800 million. So we had to go back to the US Congress and say everybody promised not to do this again. We got a plan in place, we packed it up. But as a result of that hearing, it was actually decided that, okay, at this stage of the project, you've managed to hold the budget for four or five years to this level. You can have this extra $800 million, but that's it, guys, do not come back again.

Will - You mentioned that this unfortunate development delayed launch by 18 months. Now back in 2011, you were hoping to have the JWST launched by 2018. Obviously, you have the shaking incident, but also the COVID word will be floating around. Any plans that happened around 2020 were these two factors. The reasons for the delayed launch?

Matt - I have to say full credit to the teams and everything, COVID had not such a huge delay. The biggest problem was this, trying to make sure that we had thought of everything. Retesting everything after we found these screws that fell out, there was this big push to go back and test everything. Because there are 300 single point failures in this spacecraft and we had to make sure every one would actually work. And so there's this methodical effort to go back and make sure we, we hadn't made any more mistakes in putting this thing together, that we actually understood where everything came from. You know, it is amusing because as you say, when I spoke to you, we wanted to launch this. My wife used to say to me, 'darling, when we first started this job, you're going to launch it next year and you're still trying to launch it next year'. She said, 'you're doing really well at your job.' But it worked flawlessly because of all of that.

Will - Exactly. And December 25th, it made it up into space. Now, I get nervous taking my camera on an aeroplane <laugh>, I cannot imagine how tense it must have been strapping $10 billion worth of telescope with 300 single point failures onto a rocket. How do you get something so intricate up into space in one piece?

Matt - First of all, you have people looking over your shoulder as you pack this thing up. Everybody checks everything. We had even worked out how to make holes in the fairing. So as all the air escaped, as the rocket shut up through the atmosphere and got into the vacuum of space, we even made sure that the way the air escaped from all the folds of the sunshade would not rip the sunshade. All these things that we didn't know we'd have to worry about. Five or six years later, we even worried about what temperature the spacecraft would be at. And so we had to roll the Arianne as it was actually exiting the atmosphere because the sun is like a barbecue. We had to roll it round to make sure we actually got heat evenly distributed around it, so we didn't overheat some part of it and actually cause some damage to some of the multiple joints that we have on the back sunshades. So it was a very, very complex launch process. And I have to say, Arianne did a superb job because we'd had no course corrections and it basically made it to L2, a million miles from here, with all of its fuel intact. So we actually have something like 20 years of fuel left. We had expected to use fuel on the way to actually correct it. We didn't. But of course, the problem is all of us who had actually been working on this, unfortunately the launch was only the first of holding one's breath because with the James Webb, launch is only the beginning of all the issues that we had to do. We then had to unfold it. We had to deploy this sunshade, not rip it, we had to unfold the mirror and make sure it was all working. And then we had to line all these mirror segments up to make it work as a single mirror, which means you had to line the mirrors up to less than a wavelength of light, remotely a million miles from Earth where the telescope was cooling to roughly minus 200 degrees centigrade.

Will - After all that planning and all that stress, was there a singular moment where you and the team went, 'wow, this has all worked and worked perfectly'?

Matt - I think everybody was sort of hugely relieved, mildly surprised. I think that everything went so incredibly well. But I think that's a testament to all the problems we'd had previously, that we had to go back and retest, re-examine, retest, re-examine. And that paid off on the day. So when we actually deployed the spacecraft off, we got it out to L2, we saw the mirrors for the very first time, and then we managed to line all the mirrors up for the very first time. That very first image, we had this sort of hexagonal shaped stars. The mirrors began to line up and come into phase, as we call it. The background lit up with all these points. I remember looking at this image and all the engineers asking me, what are all those points in the background? Nobody's looking at this star anymore. They go, ''oh my goodness, is that the detector not working too well, Matt, or is that this? It turns out those were galaxies, James Webb in its alignment image, the whole sky was filled with galaxies. And that's when I realised this telescope was going to work incredibly well.


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