Direct Measurements with Balloon Experiments: The High-Energy Antimatter Telescope HEAT is a sophisticated instrument for the detection and identification of positrons in the primary cosmic radiation. It was attached to a giant balloon and lifted above the Earth's atmosphere to measure particles in the energy range 1 to 50 GeV. HEAT measured precisely the electron and positron spectra but did not find evidence for enhanced antimatter in the cosmic radiation. The measurements revealed an amount of positrons that is roughly compatible with what one would expect from production by cosmic rays in the interstellar medium and constrain the models of cosmic ray transport through the galaxy. HEAT had later an antiproton and a light-ion phase.
See here a Discovery Channel program about Ballooning and HEAT: part 1, part 2
