This grant provides partial support for long-duration balloon (LDB) balloon flights and analysis of passive cosmic ray composition measurements. The experiment will be done by a collaboration known as JACEE (Japanese American Cosmic-ray Emulsion-chamber Experiment) which includes nearly 35 senior scientists at 11 institutions from the U.S., Japan and Poland. The experimental aims are to measure the cosmic ray energy spectrum and composition at ultra high energies (approaching 1015 eV) and also to study nuclear interactions at these energies, beyond the capabilities of any accelerator. No other known technique can make similar measurements. It is the expectation of the JACEE group to make 20 such LDB flights over the next 10 years. This project is jointly supported by NSF, NASA and sister agencies in Japan and Poland.
