A NASA satellite launched on 25 August 1997 carrying six high-resolution spectrometers to measure the composition and abundances of atomic particles of solar, interplanetary, interstellar, and galactic origins, spanning the energy range from a few hundred eV (solar wind ions) up to 600 MeV (galactic cosmic ray nuclei). ACE also carried three instruments to monitor energetic electrons, hydrogen and helium ions, and a magnetometer. The spacecraft occupies a halo orbit about the L1 Earth–Sun Lagrangian point from where it provides advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and endanger astronauts.