ACE (Advanced Composition Explorer)

Advanced Composition Explorer (ACE)

Advanced Composition Explorer (ACE). Credit: NASA.

Advanced Composition Explorer (ACE) is a NASA satellite designed to measure the elemental and isotopic composition of matter from several different sources, including the solar corona and the interstellar medium.


ACE was placed in a halo orbit around the first Lagrangian point (L1) of the Earth-Sun system, about 1.4 million kilometers from Earth. It carries six high-resolution sensors and three monitoring instruments for sampling low-energy particles of solar origin and high-energy galactic particles with a collecting power 10–1,000 times greater than previous experiments. The spacecraft can give advance warning, of about one hour, of geomagnetic storms that might overload power grids, disrupt communications, and pose a hazard to astronauts.

launch date Aug 25, 1997
launch vehicle Delta 7920
launch site Cape Canaveral
orbit halo
mass at launch 785 kg