Editing Advanced Composition Explorer (section)

=== Ultra-Low-Energy Isotope Spectrometer (ULEIS) ===
[[File:ACE-uleis sm.jpg|thumb|ULEIS]]
The Ultra-Low-Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra-high-resolution [[mass spectrometer]] that measures particle composition and energy spectra of elements He–Ni with energies from ~45 keV/nucleon to a few MeV/nucleon. ULEIS investigates particles accelerated in [[solar energetic particle]] events, interplanetary shocks, and at the solar wind termination shock. By determining energy spectra, mass composition, and temporal variations in conjunction with other ACE instruments, ULEIS greatly improves our knowledge of solar abundances, as well as other reservoirs such as the local [[interstellar medium]]. ULEIS combines the high sensitivity required to measure low particle fluxes, along with the capability to operate in the largest solar particle or interplanetary shock events. In addition to detailed information for individual ions, ULEIS features a wide range of count rates for different ions and energies that allows accurate determination of particle fluxes and anisotropies over short (few minutes) time scales.<ref name=mason98>{{cite journal |last=Mason |first=G. M. |title=The Ultra-Low-Energy Isotope Spectrometer (ULEIS) for the Advanced Composition Explorer |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=409–448 |doi=10.1023/A:1005079930780 |bibcode=1998SSRv...86..409M |s2cid=42297254 |display-authors=et al.}}</ref>