ULEIS Spacecraft near the sun
Our Contribution

Probing Particles Accelerated From Solar Events

Designed to measure the composition and energy range of light elements — from helium to nickel — and their isotopes, the Ultra Low Energy Isotope Spectrometer (ULEIS) provides insights into how particles are accelerated during energetic solar events, such as solar flares and coronal mass ejections.

About the Instrument

Instrument Type

The APL-built Advanced Composition Explorer, or ACE, spacecraft is a NASA mission that studies the many charged, energetic particles streaming from the Sun, the interplanetary medium, and the Milky Way galaxy. In coordination with ACE’s other instruments, the spacecraft’s Ultra-Low-Energy Isotope Spectrometer, or ULEIS, collects and measures the energy, abundance, and time variations of light elements, which include helium through nickel, to investigate how they are accelerated by large solar events, such as coronal mass ejections. Of particular interest is the relative abundance of the elemental isotopes — atoms of the same element but with a different number of neutrons — especially helium. ULEIS continues to make critical measurements of numerous solar events. It makes significant contributions to understanding the abundances of these charged particles, including helium, neon, and magnesium ions, and the mechanisms that accelerate them.

The ULEIS instrument
Image of the ULEIS instrument, which will measure rates of particle flow of the elements helium through nickel. 

Credit: NASA


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