Since that initial test, balloons have provided a unique window into the wider universe. Even though each individual balloon mission could only last a few days to a few months, they could reach altitudes far higher than any ground-based observatory — all for a fraction of the cost of space-based missions.
With balloons, astronomers have been able to easily access several regions of the electromagnetic spectrum, offering insights into the high-energy and infrared universe.
Perhaps the most significant of the balloon-born experiments was BOOMERanG, the Balloon Observations Of Millimetric Extragalactic Radiation And Geophysics. Starting in 1997, the BOOMERanG experiment flew to an altitude of 138,000 feet (42 km) above Antarctica to observe the cosmic microwave background, the leftover light from when the entire universe cooled from a plasma state when it was just 380,000 years old.
BOOMERanG made critical measurements of this background radiation that provided the information needed to demonstrate that our universe is geometrically flat, confirming a key prediction of the Big Bang theory and validating that dark energy is real.
The future is looking up
The BOOMERanG experiments ended in 2003, but their legacy continues. Antarctica provides especially fruitful ground for many kinds of astronomy thanks to the relative clarity and dryness of the air above the South Pole.
And not all balloon-borne experiments look up. The innovative ANITA (Antarctic Impulsive Transient Antenna) looked down into the Antarctic ice sheet during its series of months-long missions.
ANITA consisted of a series of radio telescopes closely monitoring the ice while suspended from a helium-filled balloon at an altitude of some 121,000 feet (37 km). If a high-energy neutrino (a ghostly particle produced during nuclear reactions throughout the cosmos) slammed into a water ice molecule, it would produce a flash of radio emission.
By recording when and where these radio flashes occurred, ANITA essentially turned the whole Antarctic continent into a giant neutrino telescope — something that would be impossible from the ground or from space.