On this day in space! Aug. 25, 1997: NASA launches Advanced Composition Explorer to track solar wind and so much more

image via Space.com

August 25, 2026, 2:00 PM

• •ACE launched from Kennedy Space Center on a Delta II rocket on Aug. 25, 1997.
• •The spacecraft operates near the Sun-Earth L1 Lagrangian point to monitor solar wind and other charged particles.
• •ACE provides continuous solar-wind observations used in NASA's space-weather early-warning system.
• •The mission was designed for up to five years but has continued operating for 29 years.
• •NASA said only one ACE instrument, the Solar Energetic Particle Ionic Charge Analyzer, stopped sending data in 2005.

NASA launched the Advanced Composition Explorer on Aug. 25, 1997, to study energetic particles moving through space. The spacecraft traveled to the Sun-Earth L1 Lagrangian point, where it continuously monitors the solar wind. Its data help scientists anticipate geomagnetic storms that can affect satellites and power grids on Earth. Originally expected to last up to five years, ACE has remained operational for 29 years with only one instrument failure reported.

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