Low cost balloon-borne telescope could rival Hubble

Durham University’s astronomers are part of an international team that has built a new kind of astronomical telescope that will be launched to the edge of space by a helium balloon the size of a football stadium.

The Superpressure Balloon-borne Imaging Telescope (SuperBIT) is a collaboration between Durham, NASA, the Candadian Space Agency and Toronto and Princeton universities. The project will be presented today (Wednesday 21 July) at the online RAS National Astronomy Meeting (NAM 2021).

SuperBIT will fly above 99.5 per cent of the Earth’s atmosphere. The telescope will make its operational debut next April and when deployed should obtain high-resolution images rivalling those of the Hubble Space Telescope.

The science goal for its 2022 flight is to measure the properties of dark matter particles. Although dark matter is invisible, astronomers map it by the way it bends rays of light, a technique known as gravitational lensing.

SuperBIT will test whether dark matter slows down during collisions. No particle colliders on Earth can accelerate dark matter, but this is a key signature predicted by theories that might explain recent observations of weirdly behaving muons.

Professor Richard Massey, of Durham University’s Department of Physics, said: “Cavemen could smash rocks together, to see what they’re made of. We’re going to use SuperBIT to look for the crunch of dark matter.

“It’s the same experiment, you just need a space telescope to see it.”

Light from a distant galaxy can travel for billions of years to reach our telescopes. In the final fraction of a second, the light has to pass through the Earth’s swirling, turbulent atmosphere and our view of the universe 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 escapes the effect of the atmosphere.

SuperBIT has a 0.5 metre diameter mirror and is carried to 40km altitude by the huge helium balloon.

Its final test flight in 2019 demonstrated extraordinary pointing stability, sufficient to thread a needle 1km away, and to hold it for an hour. This lets a telescope obtain images as sharp as those from Hubble.

Nobody has done this before, not only because it is exceedingly difficult, but also because balloons could stay aloft for only a few nights: too short for an ambitious experiment.  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 seasonally stable winds, it will circumnavigate the Earth several times – imaging the sky all night, then using solar panels to recharge its batteries during the day

Crucially, SuperBIT cost almost 1,000 times less than a similar satellite. Not only are balloons cheaper than rocket fuel, but 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 – so the development team bought the cutting-edge camera for SuperBIT’s latest test flight a few weeks before launch. This space telescope will continue to be upgradable, or have new instruments on every future flight.

Mohamed Shaaban, a PhD student at the University of Toronto, in Canada, who will be presenting the research to NAM 2021, said: “New balloon technology makes visiting space cheap, easy, and environmentally friendly. As well as building a space telescope, our team has successfully tested all sorts of electronic and mechanical systems that could be used in future satellites.”

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 Telescope due to launch this autumn), or a single optical band (like the Euclid observatory due to launch next year).

By then SuperBIT will be the only facility in the world capable of high-resolution multicolour optical and ultraviolet observations. The team already has funding to design an upgrade from SuperBIT’s 0.5 metre aperture telescope to 1.5 metres (the maximum carrying capacity of the balloon is a telescope with a mirror about 2 metres across).

Boosting light gathering power tenfold, combined with its wider angle lens and more megapixels, will make this larger instrument even better than Hubble. The cheap cost would even make it possible to have a fleet of space telescopes offering time to astronomers around the world.

News source: Durham University

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