ICE

Explorer 59, International Cometary Explorer, International Sun-Earth Explorer-3, ISEE-3

Mission Profile

ICE (International Cometary Explorer, ISEE-3, Explorer 59) is a NASA spacecraft launched on 12 August 1978 aboard a Delta 2914, originally designed as the third spacecraft in the International Sun-Earth Explorer program to study solar wind interactions with Earth's magnetosphere at the L1 Lagrange point. In 1983 mission controllers executed a series of unprecedented lunar gravity assist maneuvers to redirect ICE toward comet 21P/Giacobini-Zinner, which it flew through in September 1985 — becoming the first spacecraft to directly sample a comet's plasma environment. ICE subsequently observed comet Halley from a distance in 1986 as part of the International Halley Watch fleet. After decades of silence, citizen scientists reestablished contact with the spacecraft in 2014 as it made its final return toward Earth's vicinity, but insufficient propellant precluded orbital capture.