Scientists solve big limitation of stratospheric balloon payloads

December 01, 2020

WASHINGTON, December 1, 2020 -- Nearly all photons emitted after the Big Bang are now visible only at far-infrared wavelengths. This includes light from the cold universe of gas and dust from which stars and planets form, as well as faint signals from distant galaxies tracing the universe's evolution to today.

Earth's atmosphere blocks most of this light, and space missions are an ideal but prohibitively expensive way to explore it. So scientists are turning to huge stratospheric balloons -- the size of an entire football stadium -- because they are a tiny fraction of the cost.

In Review of Scientific Instruments, from AIP Publishing, Alan J. Kogut, of NASA's Goddard Space Flight Center, and colleagues found a way to solve a widely recognized limitation of stratospheric balloon payloads, which fly at altitudes of 130,000 feet above 99% of the atmosphere.

"To really peer into the cold universe, you need a large telescope cooled to near absolute zero, flying above Earth's atmosphere," Kogut said. "By large, I mean a telescope mirror the size of a living room. Why so cold? Heat from the telescope can wipe out images from deep space, like overexposing a camera. To see faint cold signals from deep space, the telescope must be cooled to 10 K (minus 440 F), only a few degrees above absolute zero."

It may sound simple in theory, but it is quite difficult to cool a telescope the size of a living room to nearly absolute zero while flying it from a balloon.

"Liquid helium can easily cool the telescope, but keeping it cold means putting the entire telescope into a giant thermos bottle called a dewar," he said. "A thermos bottle the size of a living room would weigh several tons -- more than even the largest balloons can carry."

This is where the Balloon-Borne Cryogenic Telescope Testbed (BOBCAT) comes in.

"BOBCAT develops technology for ultralight dewars to reduce their weight enough to allow really big ones to fly on a balloon," said Kogut.

Dewars have an inner cup holding the cold liquid, surrounded by an outer shell. The gap between them has no air within it, a vacuum, to prevent air from carrying heat from the outside world into the cold interior.

A dewar is heavy, because its walls need to hold a vacuum against sea-level air pressure. But a dewar meant to work on a balloon does not need to work at sea level. It must work at 130,000 feet above sea level, where there is almost no air pressure.

The scientists designed a dewar with extremely thin walls, not much thicker than a soda can's, which can launch at room temperature. It has a valve, so the vacuum gap between the inner cup and outer wall vents during ascent to let air out.

"Once the balloon reaches 130,000 feet, the valve closes to create a proper vacuum space, and it cools the telescope by pumping liquid nitrogen or liquid helium into the dewar from separate storage tanks," Kogut said. "The storage tanks are small and don't weigh much. Now, we have a cold telescope above the atmosphere, able to see faint images from the cold or distant universe."

The first flight was a success, and the next step is to re-fly the payload carrying an ultralight dewar.
The article, "The Balloon-Borne Cryogenic Telescope Testbed mission: Bulk cryogenic transfer at 40 km altitude," is authored by Alan J. Kogut, Thomas Essinger-Hileman, Samuel Denker, Nicholas Bellis, Luke Lowe, and Paul Mirel. The article will appear in Review of Scientific Instruments on Dec. 1, 2020 (DOI: 10.1063/5.0021483). After that date, it can be accessed at


Review of Scientific Instruments publishes novel advancements in scientific instrumentation, apparatuses, techniques of experimental measurement, and related mathematical analysis. Its content includes publication on instruments covering all areas of science including physics, chemistry, materials science, and biology. See

American Institute of Physics

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to