International Cometary Explorer

The International Cometary Explorer (ICE) spacecraft (designed and launched as the International Sun-Earth Explorer-3 (ISEE-3) satellite), was launched August 12, 1978, into a heliocentric orbit. It was one of three spacecraft, along with the mother/daughter pair of ISEE-1 and ISEE-2, built for the International Sun-Earth Explorer (ISEE) program, a joint effort by NASA and ESRO/ESA to study the interaction between the Earth's magnetic field and the solar wind.

ISEE-3 was the first spacecraft to be placed in a halo orbit at the L₁ Earth-Sun Lagrangian point. Renamed ICE, it became the first spacecraft to visit a comet, passing through the plasma tail of Comet Giacobini-Zinner within about 7,800 km (4,800 mi) of the nucleus on September 11, 1985.

NASA suspended routine contact with ISEE-3 in 1997, and made brief status checks in 1999 and 2008.

On May 29, 2014, two-way communication with the spacecraft was reestablished by the ISEE-3 Reboot Project, an unofficial group with support from the Skycorp company. On July 2, 2014, they fired the thrusters for the first time since 1987. However, later firings of the thrusters failed, apparently due to a lack of nitrogen pressurant in the fuel tanks. The project team initiated an alternative plan to use the spacecraft to "collect scientific data and send it back to Earth," but on September 16, contact with the probe was lost.