Description
The Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition
Explorer (ACE) spacecraft is intended to be a major step in
ascertaining the isotopic composition of the cosmic rays and hence a
major step in determining their origin. The Galactic cosmic rays
(GCRs) consist, by number, primarily of hydrogen nuclei (~92%) and He
nuclei (~7%). The heavier nuclei (1%) provide most of the information
about cosmic-ray origin through their elemental and isotopic
composition. The intensities of these heavy cosmic rays are very low
and progress in the past has been impeded by limited particle
collection power, particularly regarding individual isotopes. CRIS is
designed to have far greater collection power (~250 cm2-sr) than
previous satellite instruments ( < 10 cm2-sr) while still maintaining
excellent isotopic resolution up through Z=30 (Zinc) and beyond.