BARREL (Balloon Array for Radiation belt Relativistic Electron Losses) is a multiple-balloon investigation that will study Earth's Radiation Belts.
Atmospheric losses of relativistic electrons play an important role in radiation belt dynamics; precipitation into the atmosphere may even completely deplete the radiation belts in some cases.
BARREL is the first NASA Living With a Star Geospace Mission of Opportunity, and will support NASA's RBSP (Radiation Belt Storm Probes) mission.
It's been an exciting day today! Although we haven't launched any more balloons, geomagnetic activity has picked up and we observed several relativistic electron precipitation events today. We terminated payload 1O at 1138 UT due to its low altitude, so currently have five balloons in the air (though 1K is at quite high geomagnetic latitude now). We are hoping for another launch opportunity from SANAE soon and have a possible opportunity on Saturday from Halley.