ISEE, launched in 1977, was a three-satellite project with two of the satellites built by National Aeronautics and Space Administration (NASA) and the third by the European Space Agency (ESA). ISEE-1 and ISEE-2, the ESA satellite, carried overlapping instrument packages and shared a highly elliptical orbit. Together they were to resolve space-time ambiguities intrinsic to one-satellite examinations of the magnetosphere and its boundaries. The third satellite was placed in a halo orbit roughly one million miles from the earth in order to study the solar wind before it reached the other two spacecraft. The third satellite was redeployed to a cometary encounter while the two spacecraft orbiting within the magnetosphere continued to take data. The AIP Study focused on ISEE-1 and ISEE-2.
From the description of International Sun-Earth Explorer (ISEE) (Space Science): Oral history interviews, 1992-1994. (American Institute of Physics). WorldCat record id: 79843162
