On September 11, 1985, the International Cometary Explorer (ICE) will pass through the tail of Comet Giacobini‐Zinner and thus become the first spacecraft ever to intercept a comet. The ICE spacecraft was formerly known as the International Sun‐Earth Explorer Three (ISEE 3). When ISEE 3 was launched in August 1978, little thought had been given to having this spacecraft encounter a comet. In fact, ISEE 3 will have had three different mission phases during its lifetime, only the first of which was planned at the time of launch. The ISEE program originated as a joint program of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) to study the earth's magnetosphere. The role of ISEE 3 was to observe the solar wind upstream of the earth. ISEE 1 and 2 then observed the response of the magnetosphere to changes in the solar wind. This phase lasted almost 4 years and led to the exploration of the foreshock region of the earth's bow shock (see the Upstream Waves and Particles special issue of the Journal of Geophysical Research, vol. 86, pp. 4319–4536, 1981). The second phase began in late 1982, when ISEE 3 was moved from a position in front of the earth to one behind it in order to study the unexplored region of the earth's tail from the lunar distance of 60 RE to 240 RE. Results from this exploration may be found in the ISEE 3 Distant Geotail Results special issue of Geophysical Research Letters (vol. 11, pp. 1027–1105, 1984). The third and final phase, that of comet studies, began on December 22, 1983, when ISEE 3 passed within 120 km of the moon, sending it on its way out of the earthmoon system. At this time the spacecraft was renamed ICE.