ACE In Space


ACE Banner Image

Overview: Fundamental Technologies, LLC, of Lawrence, Kansas, works diligently to provide data products for the Electron, Proton, and Alpha-Particle Monitor (EPAM) instrument onboard the Advanced Composition Explorer (ACE) spacecraft. The following gives a brief explanation of the ACE Mission and the types of instruments included in its scientific payload.


Mission Background: The Advanced Composition Explorer (ACE) spacecraft was launched in August 1997. Carrying six 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.


Scientific Payload: The ACE scientific payload carries six high-resolution sensors and three

monitoring instruments: 


CRIS Cosmic rays
SIS Solar energetic particles
ULEIS Particles accelerated in solar energetic particle events
SEPICA Ionic charge states of solar and interplanetary energetic particles
SWIMS/SWICS Composition of solar and interstellar matter
EPAM Broad range of energetic particles
SWEPAM Solar wind, coronal mass ejections, interplanetary shocks
MAG Local magnetic field in the interplanetary medium
RTSW Real-time data of solar wind and energetic particles


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


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

Additional information at Fundamental Technologies, LLC:

Updated 1/2/19, Cameron Crane


*Since official launch
August 25, 1997, 14:39 UTC


Manufacturer: Johns Hopkins APL built and operates the Advanced Composition Explorer (ACE) and its instruments

Mission Duration: 5 years were originally planned, 20+ years have elapsed.

Destination: The L1 Lagrangian point between the Earth and the Sun (1.5 million km away from the Earth)

Orbit: ACE's orbit is a Lissajous orbit near the L1 Lagrangian point between the Earth and the Sun.