Fundamental Technologies


Advanced Composition Explorer
Energetic Proton and Alpha Monitor

Overview and Table of Contents

The Advanced Composition Explorer (ACE) spacecraft was launched in August 1997. Carrying 6 high-resolution sensors and 3 monitoring instruments, ACE samples low energy solar particles and high energy galactic particles and provides near real time, 24/7 continuous coverage of the solar wind and higher energy particles accelerated by the sun, from a distance of about 1.5 million km from Earth.

The EPAM (Electron, Proton and Alpha Monitor) instrument, built by the Johns Hopkins University Applied Physics Laboratory, consists of 5 telescope apertures which use the spin of the spacecraft to sweep the full sky:

2 Low Energy Magnetic Spectrometers (LEMS) Measure flux and direction of ions greater than 50 keV
2 Low Energy Foil Spectrometers (LEFS) Measure flux and direction of electrons above 30 keV
1 Composition Aperture(CA) Measures elemental composition of the ions

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Last modified March 8, 2011
T. Hunt-Ward