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Mission Overview

The primary goal of NASA's Advanced Composition Explorer (ACE) is to sample matter, in the form of energetic particles, that have originated in:

The collecting power of the instruments on the ACE spacecraft is 10 to 1,000 times greater than that of previous experiments. This greatly-increased collecting power will allow ACE scientists to study particle populations traveling near the Earth in much greater detail than ever before.

Among the particle populations being sampled by ACE are:

Solar Wind:
The solar wind is a continuous supersonic outflow of plasma from the sun.
Solar Energetic Particles:
Solar energetic particles are particles that have been accelerated in solar flares.
Pickup Ions from the Interstellar Gas:
Pickup ions are created when interstellar gas travels close to the sun. The interstellar gas is ionized by solar UV radiation and then picked up by interplanetary magnetic fields and swept away from the sun.
Galactic Cosmic Rays:
Galactic cosmic rays are particles that have been accelerated to extremely high energies by various sources in the Milky Way Galaxy. To learn more about galactic cosmic rays click here.

The information gathered by ACE is compared with that from other missions, past and present, for a better understanding of the interaction between the Sun, the Earth, and the Galaxy.

The scientific management of the ACE Mission resides with the California Institute of Technology, and the Principal Investigator is Dr. Ed C. Stone. The ACE spacecraft was built by the Applied Physics Laboratory of the Johns Hopkins University. For more information on the Mission visit the NASA GSFC ACE page or the ACE homepage at Caltech.

To learn more about ACE SEPICA, please read a paper about the instrument.