BARREL (Balloon Array for RBSP Relativistic Electron Losses)

BARREL uses stratospheric balloons to study the loss of high energy electrons from Earth's Van Allen radiation belts. The electrons in this region of near-Earth space are relativistic, moving very close to the speed of light. BARREL balloons measure x-rays produced by these particles when they are scattered into Earth's atmosphere. BARREL balloon campaigns have been conducted in Antarctica in January-February 2013 and 2014 during which 20 small (~20 kg) balloon payloads were launched, and in Sweden in 2015 (7 launches). BARREL works closely with the Van Allen Probes, two NASA satellites, launched in August 2013 to study the radiation belts.