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Country USA
Mission Comet Giacobini-Zinner Flyby
Launch Date August 12, 1978
Launch Vehicle Delta 2914
Spacecraft Mass 478 kg
Key Dates Nov 20, 1978 - Halo Orbit - Earth-Sun L1 Libration Point
Sep 11, 1985 - Comet Giacobini-Zinner Flyby
Mar 28, 1986 - Comet Halley Distant Flyby
End of Mission 2010
Comments First Ever Comet Encounter
Possible Earth Recovery in 2014

ice_s.jpg The International Sun-Earth Explorer 3 (ISEE-3) spacecraft was part of a three spacecraft mission (ISEE 1, 2 & 3) whose purpose was to study the solar wind and the solar-terrestrial relationship at the boundaries of the Earth's magnetosphere. After a series maneuvers and lunar flybys, ISEE-3 (renamed to ICE) would encounter Comet Giacobini-Zinner in 1985 and provide distance observations of Comet Halley in 1986.

Launched on August 12, 1978, ISEE-3 was placed into a halo orbit around the Sun-Earth L1 libration point, 235 Earth radii from the Earth. The three ISEE spacecraft were equipped with complementary instruments for making measurements of plasmas, energetic particles, waves, and fields (there was no camera). In 1981, it was proposed that ISEE-3 be maneuvered into Earth's magnetotail, and then later towards a comet. On June 10, 1982 the first of these maneuvers was started which moved the spacecraft out of its halo orbit around the L1 point where it has orbited for nearly 4 years. Fifteen manuevers were required through the magnetotail, along with the five lunar flybys to get the spacecraft out of the Earth-Moon system and on it way towards Comet Giacobini-Zinner. The fifth and final lunar flyby on December 22, 1983, passed only 119.4 km above the Moon's surface near the Apollo 11 landing site. At this point, the spacecraft was renamed International Cometary Explorer (ICE).

On June 5, 1985, the spacecraft was maneuvered 26,550 km behind Comet Giacobini-Zinner so that its fields and particles instruments could sample the comet's tail. On September 11, the first ever in situ cometary measurements were made as the first first ions were detected as ICE crossed a bow shock. The spaceraft found a region of interacting cometary and solar wind ions, and encountered a comet plasma tail about 25,000 km wide. Water and carbon monoxide ions were also identified, which confirmed the "dirty snowball" theory. The plasma density increased 100 times over the solar wind ambient, and the solar magnetic field was found to be wrapped around the comet nucleus. ICE approached the comet at a distance of 7,862 km at its closest approach on September 11, 1985, with a flyby velocity of 20.7 km/second. Because the spacecraft did not carry any dust protection equipment, it was expected to suffer some damage during the encounter. However, the spaceraft survived relatively unscathed, and analysis of the plasma wave data indicated an dust impact rate of about one per second, which was lower than expected.

In 1986, ICE made distant observations of Comet Halley on the sunward side of the comet. It flew by at a distance of 31 million km from the comet on March 28, 1986, and provided upstream solar wind data.

In 2014, ICE will return to the vicinity of Earth where it could possibly be captured for analysis of its exterior for dust impacts. NASA has already dontated the spacecraft to the Smithsonian Institute for display if it is recovered.

Ron Baalke, STARDUST Webmaster,
Last Updated Wednesday, 07-Jun-2000 13:50:33 PDT