ICE (for International Cometary Explorer) was a second mission of third ISEE (International Sun-Earth Explorer) spacecraft, ISEE-3. With its primary mission complete, it was sent into a solar orbit independent of Earth for flybys of two comets. A complicated route including lunar flybys was used to achieve this using the leftovers from fuel intended mainly for deployment and stationkeeping at its primary-mission L1 location. It successfully flew by Comet Giacobini-Zinner in 1985 (the first comet flyby) and Comet Halley in 1986. The spacecraft was then in a solar orbit in which it has remained. The ICE mission was terminated in 1997, but the spacecraft was contacted in 1999, 2008, and 2014, exploring the possibility of using it further, but 2014 attempts to use its propellant failed.
ISEE-3 was launched in 1978 and placed at the Earth-Sun L1 Lagrangian point, the first spacecraft to be deployed at a Lagrangian point. ISEE-3 was an element in a research effort regarding Earth's space weather, including the Sun's influence and was placed so it could monitor the approaching solar wind. Instrumentation was for particle analysis and magnetometery with an X-ray instrument that could also monitor gamma-ray bursts. This primary mission was concluded in 1981. Instruments: