This $10 billion telescope was taking blurry pictures. Sydney students fixed it

Two Sydney students have led a globally significant effort to sharpen the focus of the James Webb Space Telescope, resolving issues in an onboard instrument and boosting the capacity of the world’s most powerful observatory to find Earth-like planets in our galaxy.

Dr Louis Desdoigts spent two years as a PhD student at the University of Sydney engineering an enormous piece of software that can fix blurry images taken by the $US10 billion ($15 billion) telescope.

Fellow student Max Charles then put the solution to work, creating high-resolution images that captured the volcanic craters studding one of Jupiter’s moons and a stream of white-hot matter blasting from a black hole.

“This work brings JWST’s vision into even sharper focus,” Desdoigts said. “It’s incredibly rewarding to see a software solution extend the telescope’s scientific reach – and to know it was possible without ever leaving the lab.”

The Australian-developed tool in need of correction, the Aperture Masking Interferometer (AMI), was developed by Professor Peter Tuthill, an expert in astrophysical imaging from the University of Sydney’s School of Physics who supervised Desdoigts and Charles.

Tuthill’s instrument is a precisely engineered piece of metal that slots into one of JWST’s cameras. It boosts the telescope’s resolution by controlling disturbances that throw off its ultra-delicate measurements of light.

“James Webb has just been this outstanding triumph. It’s just knocked everything out of the park. Except one thing,” Tuthill said – his own device.

“That was a bit of a humbling moment for me because I put this instrument up there, and it was my little contribution to this huge flagship, and it didn’t work as advertised.”

At very high resolutions, images captured using AMI were blurry due to unforeseen electronic distortions. One problem was the “brighter-fatter” effect, where too much light blasts into one pixel and overflows to neighbouring pixels, blowing out measurements into fuzzier and less detailed snapshots of deep space.

Associate Professor Benjamin Pope, an extrasolar planet expert at Macquarie University who also supervised the two students, wondered if the problem could be solved by creating a computer model or “digital twin” of AMI. That’s what Desdoigts spent years programming with an enormous amount of “world-leading” code, Pope said.

“Long story short, we were able to build a computer model of how AMI works, and then by reversing that model, we could undo the blurring effects on these images,” he said.

“Part of this model is all physics, and part of it is actually machine learning.”

Charles tested the model on data captured from three cosmic objects. He focused on a spiral pattern of gas and dust blowing off a pair of stars in the Cygnus constellation, 6000 light years from Earth, and a jet of matter whipping around a black hole at the centre of a galaxy, capturing both in great detail.

The team also captured the volcanic craters and crisp edge of Jupiter’s moon, Io.

“We know very well what Io looks like because we have spacecraft that orbit Jupiter,” Charles said. “But the fact that we were able to image it so well from James Webb, which is a lot closer to Earth, showed a lot of promise.”

Fixing AMI unlocks the extraordinary instrument’s full potential in detecting super-faint objects close to extremely bright objects, including planets closely orbiting stars. The discovery of new planetary systems is closer in reach. And now the full potential of Tuthill’s instrument has been unlocked, he can take a breath.

“It’s just a relief to know that I’m not the guy who put the lemon up,” he said, adding the approach by his students could be applied to other instruments and unlock more discoveries.

“This is way more widely valuable than simply this one, ‘save your supervisor’s reputation’ moment. Almost any instrument on any telescope could benefit from the approaches that we’ve had to take here. So I’m really excited about the future.”

Since his work on the AMI model, Desdoigts has embarked on a position as a postdoctoral researcher at Leiden University in the Netherlands, a top institution for astronomy.

Charles swung by last week during a Europe trip. During a catch-up at the pub they agreed to celebrate their work by inking matching tattoos of the far-flung instrument they helped repair on their arms.

Their software fix, dubbed Amigo, was reported in two preprint studies released on Tuesday that have yet to be peer-reviewed.

The Earth-based solution is a welcome one; two months after the launch of JWST’s predecessor Hubble in 1990, NASA announced the telescope had a major flaw which had to by physically repaired by astronauts during risky spacewalks.

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