International Sun-Earth Explorer Program

The International Sun-Earth Explorer program was a NASA–ESA effort using three spacecraft to investigate interplanetary space and the connected Sun–Earth environment. NASA built ISEE-1 and ISEE-3, while ESA built ISEE-2. ISEE-3 monitored the solar wind from a Sun–Earth L1 orbit and later surveyed Earth's magnetic tail. After completing its primary mission, it was redirected and renamed International Cometary Explorer, making the first spacecraft flyby of a comet at Giacobini-Zinner in 1985.