On Aug. 25, 1997, NASA launched the Advanced Composition Explorer, or ACE satellite to study energetic particles travelling through space. [‘On This Day in Space’ Video Series on Space.com](https://www.space.com/39251-on-this-day-in-space.html)
It lifted off from Kennedy Space Center in Florida on a Delta II rocket and spent the next three and a half months making its way to its orbital post near the L1 Lagrangian point, a point of gravitational equilibrium between Earth and the sun. There, the spacecraft is monitoring the stream of accelerated particles coming from the sun known as the solar wind. ACE provides 24/7 continuous coverage of the solar wind, which lets scientists know when to expect geomagnetic storms that can disrupt communication satellites and power grids on Earth.
