... Perhaps the most interesting satellites in this group are the ones sent into distant orbits, some of them extending well past the Moon--e.g. the WIND spacecraft pictured here. Among them is a long series of IMP s (Interplanetary Monitoring Platforms) which sampled the Earth's distant magnetic environment, the magnetosphere, and the surrounding interplanetary region; IMP-8 is still returning good data, more than 20 years after its launch. ...