High Quality Content by WIKIPEDIA articles! The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission is designed to provide stereo images of the Earth's ring current. TWINS consists of two spacecraft in high-inclination Molniya orbits. Each spacecraft has on board its own energetic neutral atom imager, and its own Lyman alpha detector. The ENA imager provides indirect remote sensing of the ring current ions, and the Lyman alpha detector gives a measure of the neutral hydrogen cloud about the Earth, known as the geocorona. The TWINS instrumentation is on board non-NASA U.S. government spacecraft, as part of a mission of opportunity. The TWINS prime mission will last for two years, from 2008-2010.