The Ultra-Low-Energy Isotope Spectrometer (ULEIS) for the ACE spacecraft

The Ultra Low Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra high resolution mass spectrometer designed to measure particle com position and energy spectra of elements He-Ni with energies from similar to 45 keV nucl(-1) to a few MeV nucl(-1). ULEIS will investigate particles ac celerated in solar energetic particle events, interplanetary shocks, and at the solar wind termination shock. By determining energy spectra, mass comp osition, and their temporal variations in conjunction with other ACE instru ments, ULEIS will greatly improve our knowledge of solar abundances, as wel l as other reservoirs such as the local interstellar medium. ULEIS is desig ned to combine the high sensitivity required to measure low particle fluxes , along with the capability to operate in the largest solar particle or int erplanetary shock events. In addition to detailed information for individua l ions, ULEIS features a wide range of count rates for different ions and e nergies that will allow accurate determination of particle fluxes and aniso tropies over short (similar to few minutes) time scales.