by An astronomical telescope designed to complement the aging Hubble Space Telescope was lifted from the southern island of New Zealand on April 16, 2023. But as a sphere the size of a football stadium rose quietly and slowly over the Tauhinukorokio mountains, calls began to arrival from residents.
Local police and radio stations, however, had reported from NASA that the large helium balloon would raise the two-tonne SuperBIT telescope to 40km above sea level, over the next three hours. The mission we were involved in was to test whether a balloon-borne telescope could capture deep space images with high enough resolution to study the unknown substance, known as dark matter, which is 85% of all matter in the universe.
Subsequent observations and data analysis proved that balloon-borne experiments can be just as useful as rocket-launched ones, but are much cheaper. It is now up to scientists, government agencies and private companies to make the most of them.
For the next month, polar stratospheric winds carried SuperBIT around the world every eight days, mainly over the Antarctic ocean but brushing the top of South America. He went where the wind took him, but could look in any direction.
Every day, solar panels recharged their batteries. At night, he photographed the sky, including the Tarantula Nebula, a light source 160,000 light-years away, and galaxy clusters 20,000 times further away.
Without a tripod, SuperBIT used a gyroscope to stabilize any swings (we found the stratosphere to be remarkably steady…except in turbulence over the Andes, where SuperBIT once fell 1,000 feet). It was the first balloon-borne telescope to achieve Hubble-like performance for the short wavelengths of light visible to the human eye.
The balloon and telescope continued to work perfectly, but satellite communication links gradually failed. We think the radiation damaged the SuperBIT antennas. We could still download data by dropping a hard drive, attached to the telescope, to the ground. But ultimately, NASA wanted their balloon back, so we parachuted the telescope down to Argentina.
This was SuperBIT’s fifth flight, adding to ten years of mounting.
Advantages of a balloon
Unlike orbital missions, if balloon payloads don’t work the first time, they can be fixed and relaunched. This promotes a simple and creative design. Components that have now been proven to work in space include hair gel (to keep things in place), chicken roasting bags (to keep them warm), and parts of a bow used by Olympic archers (to let them out ).
Failure and success are learning opportunities. After each flight, we do-it-and-improve, or the technology improves. For example, since cameras have improved and become cheaper quickly, we have equipped SuperBIT with a new sensor every year. All this reduces costs.
Most of the cost of conventional spaceflight is mitigating the risk of failure. There is always a need for a compromise between safety, protecting expensive equipment and obtaining data.
If a balloon mission goes wrong, it’s usually less important, because we get the equipment back. SuperBIT was built mostly by Canadian PhD students, who have already spun off a new technology company.
Risk management for balloons is different, and NASA doesn’t always get the balance right. Waiting for “perfect” weather and the perfectly designed balloon, all launches from Texas began in 2017. A physically impossible risk calculation, such as a balloon exploding three times, was almost backed up by a program 2023.
A balloon can only burst once. But the French and Canadian space agencies, the US National Center for Atmospheric Research and the Science Research Council in the UK have proven that a balloon can be relaunched every few days. Risk assessment can be more realistic. Balloon teams can continuously test, play around and improve the process. In the case of a rocket launch, there is only one chance.
Growing international interest
Geography is important to developing a successful national balloon program. Countries with large landmasses can make short flights within their own airspace, such as Canada and the USA. Northern European countries can use the stable and reliable summer winds to extend flights across the Atlantic ocean, for example from Scotland to Canada.
Countries can also launch from the territory of partner nations around the world, for example the UK launches from Australia.
Geopolitics also influence the choice of flight path: a lesson well learned from the rogue Chinese balloon that flew over the US in 2023 and was eventually shot down. Permission is required to cross any country’s airspace, and we avoid war zones or conflict zones where the balloon could be considered a hostile target. This is one reason we ship from New Zealand.
Government interest in national balloon programs is increasing, as science has created new materials and manufacturing techniques for balloons that hold helium, extending flights from days to months. The US has reiterated its interest in a 2023 government paper and Canada, France and Sweden have established balloon programs.
The UK ran a world leading balloon program until the 1990s. When he abandoned it he lost an opportunity to train scientists and engineers in leadership roles. British teams are still often invited to join French or US satellite missions, but we do not direct or decide what is built. We foresee few technical, geographical or political barriers to the UK resuming a balloon program at the same time as its emerging rocket launches.
Balloons are pretty high
Officially, space begins 100km above sea level. But there is no magic line, and precious little atmosphere over 40km. Then, the stars stop twinkling and the sky is black. Long exposure astronomical photographs become pin-sharp and reveal faint distant objects that are obscure to astronomers on the ground.
Balloon cameras or spectrographs can also look down, and are high enough to capture observations of Earth just like those from satellites. They can also make atmospheric measurements around them, including the ozone layer in the stratosphere.
Balloons will not take the place of all rockets, as they cannot travel higher than 40km. And while helium is a finite resource, balloons are more “eco-friendly”. They require no rocket fuel during launch, nor do they contribute to increasing space debris in orbit – and at the end of their working lives, they do not burn up in the atmosphere. What’s not to like?
This article from The Conversation is republished under a Creative Commons license. Read the original article.
Richard Massey has received funding for SuperBIT from the Royal Society and UKRI Science and Technology Facilities Council.
Fionagh Thomson has done consultancy work for the UK space agency. She is an elected member of the sustainability committees for the Royal Astronomical Society and the European Astronomical Society.
