A Balloon-Borne Telescope Could Rival Hubble For A Fraction Of The Cost

It looks too fragile to carry a telescope, let alone keep one stable, but this test in 2016 was of a balloon whose super pressurization will allow it to keep telescopes aloft for months of observing. Image Credit: Richard Massey/Durham University

Having invested an estimated $10 billion and 25 years into the James Webb Space Telescope, NASA may have found a much, much cheaper way to get telescopes above the atmosphere. The project is set to launch in April 2022 – but unlike the JWST, if the telescope known as SuperBIT doesn't work perfectly the first time, there will be plenty more chances.

At 2.4 meters (7.9 feet) in diameter, the primary mirror of the Hubble Space Telescope is much smaller than the great Earth-based telescopes, but without atmospheric distortions provides a clearer view. Unfortunately not only are space telescopes expensive to launch but fixing errors is so challenging everything has to work the first time.

Balloons can reach above 99.5 percent of the Earth's atmosphere, giving telescopes almost as clear of a view as Hubble. However, two major obstacles have prevented their widespread use. In a talk at the RAS National Astronomy Meeting University of Toronto PhD student Mohamed Shaaban will present evidence that these have been overcome, opening the way to a new astronomical era.

The "Pillars of Creation" as observed from a balloon on a SuperBIT test flight. From next year, it should be able to take images like this for months at a time. Image Credit: SuperBIT team, from Romualdez et al. (2018) SPIE 10702

Winds blow balloons around a lot, causing shaking that can ruin their images. However, in 2019 a test flight proved this could be overcome, with a 50 centimeter (20 inch) mirror held steady to less than one thirty-sixth thousandth of a degree for more than an hour. The result is images like the one above.

Unfortunately, helium balloons lose pressure, and this has made for flights lasting only a few nights. SuperBIT's full name is Superpressure Balloon-borne Imaging Telescope. The first part of the name comes from NASA's new superpressure technology that allows balloons to hold onto their helium for months.

SuperBIT will launch from Wanaka New Zealand and, all going to plan, will circle the Earth 40 kilometers (24.9 miles) high several times, recharging its batteries with solar panels by day and taking images all night. If things don't work perfectly, modifications that can't be conducted remotely (like Hubble's recent switch to backup computer) can be made upon its return to the ground. The $5 million mission cost also leaves open the option of having multiple versions optimized for different uses, such as wide-field viewing.

SuperBIT prior to launch from Timmins Stratospheric Balloon Base Canada, in September 2019 for a test flight. Image Credit: Steven Benton, Princeton University

The first SuperBIT will be much smaller than Hubble, but the balloon is capable of carrying a 2-meter (6.6-foot) telescope, and a design for 1.5 meters (4.9 feet) is already in progress.

"New balloon technology makes visiting space cheap, easy, and environmentally friendly," Shaaban said in a staement. "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." In the process, astronomers hope to learn about the nature of dark matter.

For all SuperBIT's advantages, heat from the Earth will always prevent it from seeing far into the infrared, as the JWST can. Moreover, its images will face the same interference from photobombing satellites that is increasingly frustrating ground-based observers.



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