Advanced Composition Explorer (ACE) Spacecraft

Advanced Composition Explorer (ACE) Spacecraft

Courtesy of NASA

ACE is finding out about cosmic rays and space weather. Six sensors and three instruments are sampling particles both from the Sun and from outside the solar system. From a vantage point about 1/100 the distance from the Earth to the Sun (1.5 million km from Earth), ACE measures both large and small particle events including solar flares. It’s an incredibly long-lived mission which will have operated for close to 50 years by mission’s end!

August 25, 1977

L1 Halo (gravitational equilibrium between Earth and Sun) with a 58-day orbital period

End of Mission
Still operating (expected to have fuel to last until 2024)

Achieve science understanding to forecast space weather in the coming years when humans will venture beyond Earth's protective magnetic field. Provide near-real-time solar wind information over short time periods. Report space weather and provide an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts. Investigate the origin and evolution of solar and galactic matter, including composition of matter, origin of the elements, subsequent evolutionary processes, formation of the solar corona and solar wind.

ACE provides continuous 24/7 information (almost real-time) about solar wind and solar energetic particle intensities, which make up space weather. The information is used to give a one-hour advance warning to people on Earth about geomagnetic storms that could disrupt power grids or communications systems, and also warns astronauts of hazardous conditions. Over 400 academic papers have been published using data from ACE.