JWST Pioneer Passes Along Advice for Future Space Telescope Builders

After a quarter-century of development, NASA’s James Webb Space Telescope is a smashing success. But senior project scientist John Mather, a Nobel-winning physicist who’s played a key role in the $10 billion project since the beginning, still sees some room for improvement.

Mather looked back at what went right during JWST’s creation, as well as what could be done better the next time around, during a lecture delivered today at the American Astronomical Society’s winter meeting in Seattle.

The seeds for JWST were planted way back in 1989, a year before the launch of the Hubble Space Telescope. Mather said the scientists who were planning for what was initially known as the Next Generation Space Telescope took a lesson from the problems that plagued Hubble — problems that required an on-orbit vision correction. “No. 1 lesson from Hubble program was, figure out how you’re going to do this before you do it, and make sure the technologies are mature,” he said.

The JWST team designed a segmented mirror that could be folded up for launch, and then unfolded in space to create a 21-foot-wide reflective surface. An even wider sunshade blocked out the sun’s glare as the telescope made its observations from a vantage point a million miles from Earth.

Mather cycled through the new space telescope’s greatest hits — including a deep-field view with a gravitational-lensing galaxy cluster that brought even more distant objects into focus. “There is actually a single star which is magnified enough that you can recognize it in the image,” Mather said. “When we talked about this in the beginning, I thought the odds of this happening are too small. … I am completely stunned with this result.”

This JWST image highlights Earendel, a star that began shining 900 years after the Big Bang. (Credit: NASA / ESA / CSA / B. Welch et al.)

JWST has enough propellant on board to keep it in operation for 20 years or more, but Mather and his colleagues are already thinking about future space telescopes. “We have an array of wonderful telescopes coming,” Mather said. “I cannot possibly tell you all the wonderful things that are coming, so I’m just going to tell you the ones that interest me the most.”

The telescopes on the top of Mather’s list include Euclid, a near-infrared space telescope that’s due to be launched for the European Space Agency later this year; the Vera C. Rubin Observatory, a ground-based facility in Chile that’s expected to see first light in the 2023-2024 time frame; and the Nancy Grace Roman Space Telescope, a wide-field infrared survey telescope currently set for launch in 2027.

And then what? During this week’s AAS meeting, astronomers talked up the idea of building a Habitable Worlds Observatory — a space telescope capable of seeing in ultraviolet, optical and near-infrared wavelengths. The proposal capitalizes on a couple of concepts that have already been put forward for NASA’s next generation of Great Observatories: the Habitable Exoplanet Observatory, or HabEx; and the Large UV/Optical/Infrared Surveyor, or LUVOIR.

Illustration: LUVOIR space telescope
Artist’s conception of the LUVOIR space telescope. (NASA / GSFC Illustration)
Illustration: HabEx space telescope
Artist’s conception of the HabEx space telescope. (NASA / JPL / Caltech Illustration)

As currently conceived, the Habitable Worlds Observatory would take up a position in the same region of space where JWST is hanging out — but unlike JWST, it would be designed to accommodate robotic servicing and upgrades.

Mather said a lot of the details surrounding the proposed telescope’s design still have to be worked out. “What is it going to be like? Well, I don’t know. We can’t draw it yet,” he said. But there are already lessons to be learned from the JWST team’s experience.

For example, JWST weathered several strikes by micrometeoroids over the year that it’s been in service, including one strike that did significant. lasting damage to the telescope’s mirror last May. Mission managers will put limits on the telescope’s observing schedule to reduce the risk of further damage.

“I guess one of the obvious lessons learned is, since the Webb has micrometeoroid damage, better put a pipe around the telescope to protect it,” Mather said.

“Also, taking advantage of the changes of infrastructure in our world, you can have bigger rockets and more rockets,” he added. “You can put things up in pieces, put them together, service the observatory.”

Mather noted that Northrop Grumman, which built JWST for NASA, is already working on systems for in-space satellite servicing. “Whatever you want, you can ask for it,” he said. “You can send up starshades later. Anyway, there are possibilities — and I don’t know how far we can get, but we certainly should be looking for them.”

What was John Mather saying about his “scientific baby” back in 2007? Take a trip down memory lane, and read the Q&A that Alan Boyle conducted with Mather 16 years ago during an earlier AAS meeting in Seattle.