For years, the Webb telescope had a reputation as one of NASA’s most troubled programs.
Years behind schedule and billions over budget, the James Webb Space Telescope went through a near-death experience in 2011: a restructuring known as a “replan” intended to put the program back on track.
Five years later, that replan appears to still be working. JWST remains within its $8 billion budget and is on schedule for launch in October 2018 with months of margin to spare. Key elements of the telescope are being assembled now, including installation of the 18 segments that make up its 6.5-meter primary mirror, and the layers of its tennis court-sized sunshield. Concerns about the telescope’s progress have faded.
That shift was on display at a JWST “town hall” meeting during the recent conference of the American Astronomical Society in Ki s s immee, Florida. Most of the 90-minute event focused on planning for observations by the telescope after launch and science astronomers hope to achieve with it. There were no questions about the status of the telescope’s development after a brief presentation about it.
Scott Willoughby, JWST program manager for prime contractor Northrop Grumman, discussed the status of the telescope with SpaceNews during the AAS conference.
What’s the status of JWST’s major elements?
The three major things that Northrop Grumman does are the optical telescope element, the sunshield and the spacecraft bus. On the telescope, the mirrors are being installed right now, and that is terrific, because it’s really no small feat. We’re going to finish that by the end of February. We’ll then hand it over to NASA around the same time NASA completes the testing of the four instruments.
For the bus, we completed the manufacturing of the major structure at the end of last summer. What we’re doing with that structure right now is static testing. Every bonded joint on the composite structure is required to be pushed or pulled to a load that is 25 percent higher than the predicted launch load. That finishes up around the end of January, and then we start integration of some flight hardware into it. The bus is on track.
The sunshield, in terms of that higher-level assembly, I won’t say is the least mature, but it’s the one coming together at the end. The sunshield membranes, those five Kapton membranes that comprise the big, noticeably shiny part of it, two of them are delivered. It’s still on plan.
Overall, it’s one of those things that, when it goes so well, it seems understated, especially since people have been following it for many years and almost kind of look suspiciously at how great the progress has been.
What’s on the critical path now?
The cryocooler was the critical path in the summer, and then the instruments had some rework and they were the critical path. I think the bus tied the instruments for a couple of weeks. Now the sunshield is the critical path. They’re within about a month of each other. We have about eight months of margin still remaining until that October 2018 launch date.
Is that eight months of margin what you were projecting to have at this point?
Yes. It’s kind of hard to predict how that margin is going to get burned, but certainly when we distributed the margin we would have expected to be at about this point right now. In fact, we’re doing slightly better.
Some have raised concerns you might not have enough margin to cover problems when the project enters the integration and testing phase.
We have about a month per year of margin in this development and production time, because something can lose more than that, but since you have a bunch of pieces, it’s easier to move them around. As you get closer and closer to integration and testing, you have less flexibility to move everything around. So the standard that we measure ourselves against is two months per year when we get there.
We need more margin when we get into the back end: it’s not just one linear burn from the start of the replan in 2011 until launch in 2018. We’re still holding above the line with eight months of margin with less than three years to go. That’s a very healthy state for the program.
Is there any part of the project that you worry about more than the others?
There are two things. One is deployments of telescope components: getting to a state where we proof out the design of how each mechanism comes together. A second one is that, thermally, we’re running a telescope that is going to be at cryogenic temperatures on the optics side, while the bus is at 185 degrees Fahrenheit (85˚ C) as it sits in the sun. So those two things are the challenges that our engineers had to overcome. We’ve made good progress.
I won’t say it keeps me up at night, because I know we have a good plan, but every day when you get up in the morning you want to know how well testing went yesterday.
You mentioned that people look almost suspiciously at how well things are going. Do you notice a change in perception about JWST now that it’s been several years since the project was replanned?
Three years ago, the sentiment was, okay, are you really going to be there? Because we weren’t showing mirrors going into a backplane, we didn’t have two of the f light sunshield membranes, and we didn’t have a flight structure under static test. Now they can go on a website and see a robotic arm at any point in time hovering over the telescope with a flight mirror. The sentiment has absolutely shifted.
Are you thinking ahead to future space telescopes, and any lessons you might want to apply if you are involved in one of those future missions?
In terms of where the future missions are going, and what science they’re after, that’s not my job. I don’t spend much time on that. But the other part of your question, the lessons learned, that type of collection is absolutely my responsibility. We’re building the lessons learned into either our production methodologies or our engineering design techniques.
We have designed and developed, obviously with NASA, an optical bench that can fly a million miles away from Earth and in this case look 13.5 billion years back in time. To do that, and be thermally and dynamically stable, are very challenging engineering feats. We know how to do that now. We know the tricks of the trade of, say, how the star trackers should work or the reaction wheels or the control system.
Do you talk much with the people who will use JWST once it’s launched?
My everyday job is running the schedule and the cost control meetings: program management 101 stuff. I don’t get to often talk to the people who will use it. It’s one of the biggest reasons I come to this conference, to get that inspiration of meeting with the people who are going to use it. I can go around and talk to the students, and run into some student who says they’re already counting on Webb to fill in the next step in their research.