On Sept. 11, 1985, the International Cometary Explorer, or "ICE" became the first spacecraft to fly by a comet.<br /><br />Originally launched as the International Sun-Earth Explorer-3 in 1978, ICE was one of three spacecraft built for the International Sun-Earth Explorer (ISEE) program, a joint effort by NASA, the European Space Research Organization and the European Space Agency.<br />The program's purpose was to study space weather, or the interaction between the Earth's magnetic field and the solar wind.<br />After completing its original mission, the spacecraft did a maneuver to steer it toward comet Giacobini-Zinner. It flew straight through the comet's plasma tail, but it didn't stop there! Six months later, it flew by Halley's comet, too.
