Five weeks after rocketing off the Earth, two Canadian components that are crucial to the operations and success of the James Webb Space Telescope are set to face their first big test.
On Friday morning, the Fine Guidance Sensor (FGS) and the Near Infrared Imager and Slitless Spectrograph (NIRISS) were switched on for the first time since the mammoth astronomical satellite was launched on Christmas Day. Both instruments were built in Ottawa by the Canadian aerospace company COM DEV, which has since become part of Honeywell International.
The successful activation of the instruments was announced by the Canadian Space Agency, which is a partner in the joint North American-European project. It marks a major milestone for the agency as well as the Canadian scientists and engineers who first began working on the project more than two decades ago – and who now hope the momentum it generates will propel Canada to commit to a future space telescope of its own.
“It’s taken way longer than anyone believed possible but here we are,” said John Hutchings, an astronomer who was principal investigator for the Fine Guidance Sensor when it was first proposed as Canada’s contribution to the NASA-led project.
With a price tag of US$10-billion, Webb is, by far, the largest and most expensive piece of astronomical hardware ever sent to space. Canada’s share, which tops $130-million, works out to only a tiny fraction of the total cost of the project, though it is the largest amount the country has ever invested in space-based astronomy.
The contribution is also about as critical as it gets. NIRISS is seen as key to the telescope’s quest to characterize the atmospheres of planets in other solar systems, one of its most anticipated science goals. And if the Fine Guidance Sensor were to fail, the telescope would be unable to hold its gaze steadily enough to capture revealing images of the deep cosmos and a host of other celestial objects on astronomers’ wish lists.
“Everything had to work up to this point and it has, so mostly it’s been a great relief, but we’re not there yet,” said Dr. Hutchings, who is officially retired from the Herzberg Astronomy and Astrophysics Research Centre in Victoria, but remains active in the research community.
Earlier this week, the telescope arrived at its destination, known as L2, an unoccupied point in space about one million kilometres from Earth. It’s here that gravitational forces balance with the telescope’s motion to keep it in the same position relative to Earth as it orbits the sun.
With its sun shield and mirrors now fully deployed, the telescope has been busy shedding heat. This is essential in order for it to reach a temperature below -233 C, allowing the telescope’s sensitive instruments to discern the faint glow of infrared light emanating from distant objects in the universe.
Before that threshold is reached, operators will use the FGS in the coming weeks to help align and calibrate the 18 hexagonal segments that make up the telescope’s 6.5-metre diameter main mirror, so that they can operate as a single unit and achieve the sharpest possible images.
“For me, the big-ticket item is when we close the loop between the guidance system and the attitude control system,” said Erick Dupuis, director of Space Exploration Development at the Canadian Space Agency. “This is when we’re going to start pointing the spacecraft using the FGS – and this is what it was designed for.”
Once all the instruments are fully checked and operational – a process that is expected to take another four to five months – the FGS will use stars as guideposts to make sure the telescope stays precisely on target while it acquires its images. As long as at least three stars are in its field of view at any time, the Canadian sensor can keep the telescope from drifting off target.
Dr. Hutchings said that a key moment in the telescope’s history happened early on, when he and his colleagues convinced NASA that the FGS needed only to spy a patch of sky less than one tenth the diameter of the full moon to fulfill its task. This is because the instrument’s infrared camera can perceive cool, red stars that are plentiful in the sky but too dim to be seen at optical wavelengths. The realization reduced the size of the FGS and made for a better configuration of all the telescope’s detectors.
David Aldridge, a program manager and engineer with Honeywell, was among the few Canadian team members who saw the telescope lift off at Kourou, French Guiana, last month. This week he was at the Space Telescope Science Institute in Baltimore, where he was on hand for Friday’s start up of the telescope’s Canadian hardware.
He said that despite witnessing the telescope’s successful ascent and all the hurdles it has cleared since then, he still experienced “a little bit of nervous energy” this week before the Canadian components were activated.
Now that both FGS and NIRISS are awake, approximately 30 team Canadian team members from Honeywell, the Canadian Space Agency and participating universities will be on round-the-clock shifts at the institute over the next several weeks, he said.
“We basically need to provide a full 24 hours a day, seven days a week to monitor and participate in all the alignment activities … everything that’s going on.”
In return for Canada providing the instruments, Canadian astronomers have a guaranteed share of the telescope’s observing time.
Pauline Barmby, an astronomer at the University of Western Ontario, said that will translate into an abundance of opportunities for the country’s astronomical community, fulfilling a goal that has been central to its long-term plans for more than a decade. Other projects still lie ahead, including participation in a European Space Agency-led mission called Euclid, which will seek to understand the nature of dark energy, a mysterious phenomenon that is causing the expansion of the universe to accelerate.
“Of course, it would be amazing for Canada to spearhead its own large-scale space astronomy project,” she said.
Dr. Barmby co-led a report, released last year, that identified such a project as the top priority for Canadian astronomy for this decade. Dubbed CASTOR, the project is being developed by Dr. Hutchings among others.
CASTOR would involve a space telescope with a one-metre diameter mirror. Though small compared with Webb, which sees only infrared light, the Canadian project would play a complementary role by observing the distant universe at blue and ultraviolet wavelengths.
Buoyed by the long-awaited arrival of Webb, Dr. Hutchings said he and other team members are looking to the 2023 federal budget as an opportunity to win funding for CASTOR through the Canadian Space Agency.
“The agency is putting quite at bit of money into technical studies … and we have hopes that it will be the next big thing,” he said.
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