Project for GEOTAIL observation of the elemental and isotopic abundances of heavy energetic particles in solar flares and galactic cosmic rays

GEOTAIL spacecraft, part of the ISTP program, is scheduled to be launched in 1992. It includes a package of High Energy Particle instruments (HEP). Two instruments called MI (Medium Energy Isotope Telescope) and HI (High Energy Isotope Telescope) among the HEP instruments will be dedicated to measure elemental and isotopic compositions in SEPs and GCRs. These two instruments have the following key features; exceptionally high sensitivity, excellent isotope resolution and wide dynamic ranges of energy and species. These features can be realized by the Si detector telescopes by the use of newly developed position-sensitive detectors with a good position response and by the use of very large Si wafers.