A balloon the size of a football stadium could help astronomers get crystal-clear shots of space for a fraction of the cost of an orbital telescope like Hubble.
The secret weapon behind the SuperBIT project is a simple helium balloon – albeit one that floats up to 25 miles (40km) above the surface of the Earth and expands to a football-stadium size when fully inflated.
Developed by a consortium of researchers from the UK, US and Canada, SuperBIT (the Superpressure balloon-borne imaging telescope) is an attempt to combine the best of both worlds of orbiting and earth-bound astronomy.
Conventional ground-based telescopes have to deal with the fact that the atmosphere is very good at sustaining all human life, but annoyingly bad at letting through light from space without distorting it, making it hard to take clear pictures of astronomical objects. Orbital telescopes, like the Hubble space telescope, avoid that problem, but cost billions of dollars to assemble, launch and operate.
By placing a telescope on a platform suspended underneath an enormous balloon, the SuperBIT team hopes to get pictures as clear as a space telescope, but all for a budget of just $5m (£3.7m). “New balloon technology makes visiting space cheap, easy, and environmentally friendly,” said Mohamed Shaaban, a PhD student at the University of Toronto, and one of the researchers behind the project.
A superpressure is similar to a conventional weather balloon, but rather than using an elastic skin which can expand and contract with the contents, it keeps the helium within ever so slightly pressurised compared with the external environment. That allows the balloon to stay aloft for months, with vary little vertical movement – perfect for an astronomical programme.
Its final test flight in 2019 demonstrated “extraordinary pointing stability”, the SuperBIT team says, “with variation of less than one thirty-six thousandth of a degree for more than an hour”. That should allow a telescope to obtain images as sharp as those from the Hubble space telescope.
When the SuperBIT’s balloon is launched from Wanaka, New Zealand, next April, it will circumnavigate the Earth several times, taking pictures all night before recharging its batteries during the day. Eventually, it will return to Earth, but even that brings benefits: the design can be tweaked and improved over time, where conventional orbital telescopes are prohibitively expensive to upgrade.
“SuperBIT can be continually reconfigured and upgraded,” Shaaban added, “but its first mission will watch the largest particle accelerators in the universe: collisions between clusters of galaxies.” Those collisions should cast some light on the properties of dark matter, thought to make up most of the mass in the universe but impossible to identify except by its gravitational affects on conventional matter.
“Cavemen could smash rocks together, to see what they’re made of,” added Prof Richard Massey of Durham University, another of the project’s members. “SuperBIT is looking for the crunch of dark matter. It’s the same experiment, you just need a space telescope to see it.”