NASA's Advanced Composition Explorer (ACE) collects and analyzes particles of solar, interplanetary, interstellar and galactic origins. The data contributes to our understanding of the Sun, its interaction with Earth, and the evolution of the solar system.
- ACE continues to provide space weather reports and warnings of geomagnetic storms that can disrupt communications on Earth and harm astronauts in space.
- The spacecraft has operated far beyond its expected lifetime.
Aug. 25, 1997: Launch
Jan 21, 1998: Spacecraft began operations
NASA's Advanced Composition Explorer (ACE) spacecraft was designed to study spaceborne energetic particles from the Sun-Earth L1 Lagrange point, about 870,000 miles (1.4 million kilometers) from Earth.
Specifically, the spacecraft was launched to investigate the matter ejected from the Sun to establish the commonality and interaction between the Sun, Earth and the Milky Way galaxy.
In addition, ACE also provides real-time space weather data and advanced warning of geomagnetic storms. ACE’s nine instruments have a collecting power that is 10 to 10,000 times greater than anything previously flown.
After launch, the spacecraft’s Delta 2 launch vehicle’s second stage reignited after four hours to insert the satellite into a 110 × 851,000-mile (177 × 1.37 million-kilometer) orbit.
After reaching apogee a month after launch, ACE inserted itself into its Lissajous orbit around the L1 point. The spacecraft was declared operational Jan. 21, 1998.
As of 2015, it continued to provide near-real-time 24/7 coverage of solar wind parameters and to measure solar energetic particle intensities.
With the exception of the SEPICA instrument (data from which was no longer received after Feb. 4, 2005), all instruments on ACE remained operational as of mid-2017, and the propellant on the spacecraft could theoretically allow the mission to continue into 2024.