Complex sentence: On June 10,1982, after completing its original mission, ISEE-3 was renamed the International Cometary Explorer (ICE) and given a new mission: to study the interaction between the solar wind and a cometary atmosphere.
Split into simpler sentences: On June 10,1982, after completing its original mission, ISEE-3 was repurposed. The primary scientific objective of ICE was to study the interaction between the solar wind and a cometary atmosphere.