While the Hubble Space Telescope is back to full science operations after a computer glitch sidelined it for weeks, the pioneering 31-year-old observatory won’t last forever in space. Most of the attention about “successors” falls on the $8 billion USD ($10 billion CAD) NASA James Webb Space Telescope, which may launch this year with Canadian technology to a Lagrange point.
But cheaper alternatives are emerging, too. A Canadian-funded astronomical telescope called SuperBIT (Superpressure Balloon-borne Imaging Telescope) is expected to make its first operational high-altitude flight on a balloon in April 2022, obtaining high-resolution images at 40 km – above most of Earth’s atmosphere.
The Canadian Space Agency, NASA’s Jet Propulsion Laboratory and three universities (Toronto, Durham and Princeton) are all involved in SuperBIT; on the Canadian side, CSA awarded a nearly $300,000 grant to the University of Toronto in March 2020 for stratospheric balloon telescopes. Researchers revealed more research program details at the virtual Royal Astronomical Society’s (RAS) national astronomy meeting on Wednesday (July 21).
The resulting SuperBIT images from above 99 percent of the Earth’s atmosphere will “rival” those of Hubble’s from low Earth orbit, according to the researchers, and the observatory was built for a mere fraction of the cost of Webb – just $5 million USD ($6.3 million CAD).
Don’t be fooled by the low cost, however. SuperBIT takes advantage of emerging balloon technology to get the most light possible in its 0.5 m diameter mirror. We’ve used high-altitude balloons for astronomy before, but over time the helium leaks and long-range observations are thus difficult. NASA, however, has a new kind of “superpressure” balloon that can contain helium inside for months, allowing the telescope to stay aloft for lengthy observations.
SuperBIT’s balloon will be the size of a Canadian or United States football stadium. It will launch from Wanaka, New Zealand and circle the globe several times during its mission. At night it will watch the sky, and during the day it will recharge its batteries using solar panels.
Early tests of the balloon show a lot of promise for the debut operational flight. In 2019, for example, the researchers achieved pointing stability of less than one 36-thousandth of a degree for more than an hour, rivaling the sharp images we receive from Hubble.
“New balloon technology makes visiting space cheap, easy, and environmentally friendly,” stated Mohamed Shaaban, a PhD student at the University of Toronto, in an RAS press release. “SuperBIT can be continually reconfigured and upgraded, but its first mission will watch the largest particle accelerators in the universe: collisions between clusters of galaxies.”
These collisions are a proxy for astronomers to better understand the properties of dark matter particles, which (due to their invisibility in conventional telescopes) are best visible through gravitational lensing. Galaxies are rich in dark matter due to their large size, so SuperBIT’s first campaign will assess whether dark matter slows down when galaxies collide.
“No particle colliders on Earth can accelerate dark matter, but this is … predicted by theories that might explain recent observations of weirdly behaving muons,” RAS said in the release. The University of Toronto added that studying weak gravitational lensing in the galaxy clusters will “infer the presence and relative quantity of dark matter in these clusters as well as the large scale structure of the universe.”
SuperBIT’s long-range observations of dark matter will thus allow scientists to make more sense of the universe, as they seek statistical validity in their work. Astronomy is already pivoting more to items like all-sky surveys, which pick up a range of objects in a wide field of view, allowing scientists to put galaxies or stars in a broad context. With telescope time at a premium, the more eyes on the sky, the better.
Flying observatories are fairly rare, and sometimes they are tough to fund despite their lower cost. The NASA-German Space Agency (DLR) Stratospheric Observatory for Infrared Astronomy (SOFIA) observatory that flies aboard a modified 747, for example, is once again facing cancellation in NASA’s 2021 budget for the third time in eight years. SOFIA is famous for capturing eclipses of Pluto, Saturn’s moon Titan and one of the New Horizon’s flyby targets, MU69, to pick up more details of their atmospheres. Its observing campaigns can only run for 10 hours, however, due to the fuel capacity of its carrier aircraft.
SOFIA costs $85 million USD ($106 million CAD) a year. NASA said the science return has been too low to justify the cost, adding that Webb’s infrared capabilities will help cover some of the spectrum in which SOFIA observes. “Dramatic improvement in SOFIA’s scientific productivity is not expected,” NASA noted in its 2022 budget request. “The nature of the program, which relies on observations using an expensive platform with expensive consumables, results in low cost efficiency compared to most observatories.”
Happily, SuperBIT does have funding secured for an upgrade – though the source was not revealed in the press release. A future version of SuperBIT will fly a 1.5-metre telescope, and perhaps it could grow even bigger in the future because the balloon can carry an observatory with a mirror of up to 2 metres across, the team said.
SOFIA, SuperBIT and other flying telescopes share another huge advantage over satellites, in that they regularly return to Earth. Engineers can thus upgrade, repair or test out equipment taking advantage of the latest technology. For example, digital camera technology changes so quickly that the SuperBIT team bought their latest camera just weeks before the 2019 launch, researchers said in the release.
With Webb only operating in the infrared, SuperBIT’s capability to gather multicolor optical and ultraviolet observations is comparable to Hubble already, the team argues. Scientists hope to take advantage of increasing megapixel numbers in digital cameras to continue boosting SuperBIT’s observations, too.
So far, SuperBIT performed test flights in 2015 from Timmins, Ont., 2016 from Palestine, Texas, and 2018 from Palestine once more. (A 2017 campaign was aborted due to technical and weather issues.) The 2022 operational flight will last for about a month, according to the University of Toronto, and the data gathered will likely assist other ground telescopes with their work.
“As demonstrated by numerous test flights, the survey data generated by SuperBIT is expected to have similar quality and data collection efficiency as the Hubble Space Telescope while complementing surveys from other up-and-coming observatories such as the James Webb Space Telescope, the Vera C. Rubin Observatory, and the Nancy Grace Roman Space Telescope (formerly WFIRST),” the University of Toronto stated.
Growth opportunities in ballooning will depend on funding, of course. A 2020 to 2030 “roadmap” from the Scientific Balloon Roadmap Program Analysis Group at NASA recommends that future funding at the agency consider four key metrics: continuing to evolve super-pressure balloon technology to aim for 100-day flights, growing the launch facility at Wanaka, providing more opportunities in planetary and Earth science (as these are limited), and adding high-altitude ballooning to NASA’s workplace recruitment and development initiatives.
“Scientific ballooning has progressed in a continuous arc from early beginnings in the late 18th century … to our current era where almost every branch of astrophysics, space science, Earth science, and planetary science garner contributions from balloon missions,” the report authors noted. “There is every reason to believe that this rate of scientific productivity will continue its remarkable trajectory into and beyond the next decade.”