SuperBIT in flight

Helium balloon-lifted space telescope could be cheap rival for Hubble

Image credit: SuperBIT team

A low-cost space telescope that can obtain high-resolution images rivalling those of the Hubble Space Telescope is scheduled to set sail above the Earth’s atmosphere from April 2022.

Developed by Nasa and the Canadian Space Agency, the 'Superpressure Balloon-borne Imaging Telescope' (SuperBIT) flies above 99.5 per cent of the Earth’s atmosphere and is carried by a helium balloon the size of a football stadium.

While light from distant galaxies can travel for billions of years to reach our telescopes, once it reaches the Earth’s turbulent atmosphere the view becomes blurred.

Observatories on the ground are built at high altitude sites to overcome some of this, but until now only placing a telescope in space can escape the effects of the atmosphere completely.

The SuperBIT has a 0.5 metre diameter mirror and will be carried to a 40km altitude by a helium balloon with a volume of 532,000 cubic metres, about the size of a football stadium.

Its final test flight in 2019 demonstrated that it could be pointed at specific points in the sky with high stability – monitored for more than one hour, the lens deviated by less than one thirty-six thousandth of a degree. The team behind the telescope believe that this level of stability should enable it to obtain images as sharp as those from the Hubble Space Telescope.

The telescope on the ground

Previous efforts for similar telescopes held aloft by balloons were deemed too difficult as they could stay aloft for only a few nights at a time before needing to refuel. However, Nasa recently developed ‘superpressure’ balloons able to contain helium for months. SuperBIT is scheduled to launch on the next long duration balloon, from Wanaka, New Zealand, in April 2022.

Carried by seasonal winds, it will circumnavigate the Earth several times - imaging the sky all night, then using solar panels to recharge its batteries during the day.

With a budget for construction and operation for the first telescope of $5m (£3.6m), SuperBIT cost almost 1,000 times less than a similar satellite. Balloons are also cheaper than rocket fuel and the ability to return the payload to Earth and relaunch it means that its design has been tweaked and improved over several test flights.

Satellites must work first time, so typically have (phenomenally expensive) redundancy and decade-old technology that had to be space-qualified by the previous mission.

Modern digital cameras improve every year, which has meant the development team could attach cutting-edge cameras for SuperBIT’s latest test flight a few weeks before launch. This space telescope will continue to be upgradable and have new instruments on every future flight.

In the longer term, the Hubble Space Telescope will not be repaired again when it inevitably fails. For 20 years after that, ESA/NASA missions will enable imaging only at infrared wavelengths (like the James Webb Space Telescope due to launch this autumn), or a single optical band (like the Euclid observatory due to launch next year). This will leave SuperBIT as the only facility in the world capable of high-resolution multicolour optical and ultraviolet observations, Nasa said.

“New balloon technology makes visiting space cheap, easy and environmentally friendly,” said Mohamed Shaaban, a PhD student at the University of Toronto who is working on the project. “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.”

The science goal for the 2022 flight is to measure the properties of dark matter particles. Although dark matter is invisible, astronomers map the way it bends rays of light, a technique known as gravitational lensing. SuperBIT will test whether dark matter slows down during collisions.

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