Ultra Low Energy Isotope Spectrometer
(ULEIS)

The Ultra Low Energy Isotope Spectrometer (ULEIS) measures ion fluxes over the charge range from He through Ni from about 20 keV/nucleon to 10 MeV/nucleon, thus covering both suprathermal and energetic particle energy ranges. Exploratory measurements of ultra-heavy species (mass range above Ni) are also being performed in a more limited energy range near 0.5 MeV/nucleon. ULEIS studies the elemental and isotopic composition of solar energetic particles, and the mechanisms by which these particles are energized in the solar corona. ULEIS also investigates mechanisms by which supersonic interplanetary shock waves energize ions.

A cross section of the ULEIS telescope is shown here. The instrument is a time-of-flight mass spectrometer that identifies incident ion mass and energy by simultaneously measuring the time of flight, t, and the residual kinetic energy, E, of particles that enter the telescope cone and stop in one of the array of seven silicon solid-state detectors (SSDs) at the back of the telescope. The time of flight is measured twice by two START and a single STOP pulse from chevron microchannel plate (MCP) assemblies that detect secondary electrons that are emitted from the entrance and middle foils and the front surface of the SSDs, respectively, when the ion passes through them. These secondary electrons are accelerated to about 1 kV and deflected onto the MCPs by eletrostatic mirrors. The design of the secondary electron optics yields isochronous (equal in time) flight paths for all secondary electrons emitted normally from the foil or detector surface. The measured energy, E = 1/2 M V ², and the velocity, V = L/t (where L is the path length in the telescope), are combined to yield the mass of the ion, M = 2 E (t/L) ², and the energy-per-nucleon, E/M, inside the telescope. The ion incident energy is obtained after correcting for the energy loss in the entrance foil. The telescope view cone points in the sunward hemisphere at an angle of 60 ° to the spacecraft spin axis (which is pointed to within 20 ° of the sun).

ULEIS photo 49 KB JPEG

ULEIS photo 41 KB JPEG

The ULEIS instrument mass is 17.4 kg, its power is 17.7 W, and it has a telemetry rate of 1000 bits/sec.

ULEIS was built by the Space Physics Group, Department of Physics at the University of Maryland (UMD) and the Applied Physic Laboratory (APL) of the Johns Hopkins Univerity (JHU).

ULEIS Scientists are:


Dr. Robert Gold (APL/JHU)

Dr. Glenn Mason (UMD)


Dr. Joe Mazur (Aerospace Corp.)