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Advanced Composition Explorer
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<p>Advanced Composition Explorer (ACE or Explorer 71) is a <a href="/facts/NASA/TIMCV0yV">NASA</a> <a href="/facts/Explorer_program/UAWJXqxP">Explorer program</a> satellite and <a href="/facts/Space_exploration/2eKXYVdq">space exploration</a> mission to study <a href="/facts/Matter/osyc04UN">matter</a> comprising energetic particles from the <a href="/facts/Solar_wind/BvuB3dT8">solar wind</a>, the <a href="/facts/Interplanetary_medium/lnUR4gHd">interplanetary medium</a>, and other sources. </p><p>Real-time data from ACE are used by the <a href="/facts/National_Oceanic_and_Atmospheric_Administration/IvcuqNJg">National Oceanic and Atmospheric Administration</a> (NOAA) <a href="/facts/Space_Weather_Prediction_Center/LVcA59n3">Space Weather Prediction Center</a> (SWPC) to improve forecasts and warnings of <a href="/facts/Solar_storm/WaS5uLv4">solar storms</a>. The ACE <a href="/facts/Robotic_spacecraft/Frlbbkvu">robotic spacecraft</a> was launched on 25 August 1997, and entered a <a href="/facts/Lissajous_orbit/qgxn5sUn">Lissajous orbit</a> close to the <a href="/facts/Lagrange_point/XCAN4o3P">L1</a> <a href="/facts/Lagrange_point/XCAN4o3P">Lagrange point</a> (which lies between the <a href="/facts/Sun/CadPCVHh">Sun</a> and the <a href="/facts/Earth/HLLmDfj0">Earth</a> at a distance of some 1,500,000 km (930,000 mi) from the latter) on 12 December 1997. The spacecraft is currently operating at that orbit. Because ACE is in a non-<a href="/facts/Keplerian_orbit/XvdtxmKl">Keplerian orbit</a>, and has regular station-keeping maneuvers, the orbital parameters in the adjacent information box are only approximate. </p><p>As of 2023<a href="https://en.wikipedia.org/w/index.php?title=Advanced_Composition_Explorer&action=edit">[update]</a>, the spacecraft is still in generally good condition. NASA <a href="/facts/Goddard_Space_Flight_Center/WfoEKknM">Goddard Space Flight Center</a> managed the development and integration of the ACE spacecraft. </p>