Spacecraft in space.

Artist's concept of ISEE/ICE.

Goals: International Sun-Earth Explorer-3 (ISEE-3) was to investigate the solar wind and its interaction with Earth's magnetic field, among other phenomena in interplanetary space. It was later renamed International Cometary Explorer (ICE) and used to study two comets during an extended mission.

Accomplishments: ISEE-3 conducted the first deep survey of Earth's magnetic tail. Then, after a series of complex flybys of the Moon, the spacecraft was renamed the International Cometary Explorer (ICE) and became the first spacecraft to fly past a comet (Giacobini-Zinner). Its observations supported the theory that comets are "dirty snowballs." The following year, it joined international exploration of Comet Halley by providing data on the solar wind approaching the comet.

12 Aug 1978: Launch
20 Nov 1978: Entered Halo orbit at Lagrangian Libration Point 1 (L1)
22 Dec 1983: Entered Heliocentric Orbit
11 Sep 1985: Traversed Plasma Tail of Comet Giacobini-Zinner
1 Mar 1986: Comet Halley Observations

Mission Type: Flyby, Orbiter
Launch Vehicle: Delta 2914 (no. 144 / Thor no. 633)
Launch Site: Cape Canaveral, USA, Launch Complex 17B
NASA Center: Goddard Space Flight Center
Spacecraft Mass: 479 kg
Spacecraft Instruments: 1) solar wind plasma experiment; 2) magnetometer ; 3) low-energy cosmic-ray experiment; 4) medium-energy cosmic-ray experiment; 5) high-energy cosmic-ray experiment; 6) plasma waves experiment; 7) protons experiment; 8) cosmic-ray electrons experiment; 9) X-rays and electrons experiment; 10) radio mapping experiment ; 11) plasma composition experiment; 12) high-energy cosmic-rays experiment and 13) ground-based solar studies experiment
Spacecraft Dimensions: 16-sided body 1.7 meters in diameter, 1.6 meters high
Spacecraft Power: solar cells
Maximum Power: 173.0 W (nominal power)
Maximum Data Rate: Nominally 2048 bps during the early part of the mission, and 1024 bps during the Giacobini-Zinner encounter. The bit rate finally dropped to 64 bps (on 12/27/91)
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center,

Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

ISEE-3 was the third of three International Sun-Earth Explorers (ISEE) designed and operated by NASA in cooperation with the European Space Agency. NASA built the first and third spacecraft, while ESA built the second. The three spacecraft were to simultaneously investigate a wide range of phenomena in interplanetary space.

On 20 November 1978, ISEE-3 was successfully placed into a halo orbit at Lagrangian libration point 1 (L1), a point 1.5 million kilometers from Earth toward the Sun. At L1, Earth's gravity counterbalances that of the Sun such that an object at that location takes one Earth year to orbit the Sun, despite having a distance from the Sun that normally would require a faster orbit. The object thus remains directly between Earth and the Sun. ISEE 3 was the first spacecraft to be put into orbit around a libration point, and also the first spacecraft to monitor the solar wind approaching Earth.

ISEE-3 completed its primary mission in 1981, but Goddard Space Flight Center scientists proposed sending the spacecraft through Earth's magnetic tail and into position to intercept a comet. By 10 June 1982, the spacecraft began to use its thrusters to move into the geotail. ISEE-3 completed the first deep survey of Earth's magnetic tail and detected a huge plasmoid of electrified gas that was ejected from Earth's magnetosphere.

Subsequently, after a series of five complex flybys of the Moon (the last on 22 December 1983 at a range of only 120 kilometers), ISEE-3 was sent on a trajectory to encounter Comet Giacobini-Zinner. At this point, the spacecraft was renamed the International Cometary Explorer (ICE). On 11 September 1985 at 11:02 UT, ICE passed within 7,862 kilometers of the comet's core, becoming the first spacecraft to fly past a comet. The spacecraft returned excellent data on the comet's tail, confirming theories that comets are essentially "dirty snowballs," with surface material sleeting off during motion.

ICE also flew to 40.2 million kilometers off the sunward side of Comet Halley on 28 March 1986 and provided upstream solar wind data.

NASA headquarters approved an update to the ICE mission in 1991: a heliospheric mission consisting of investigations of coronal mass ejections in coordination with ground-based observations, continued cosmic ray studies, and special period observations such as when ICE and Ulysses were on the same solar radial line. By May 1995, ICE was being operated with only a low duty cycle, with some support being provided by the Ulysses project for data analysis. Two years later, on May 5, 1997, NASA authorized termination of operations.

ICE remains in heliocentric orbit at about 1 AU. On 10 August 2014, ICE will return to the vicinity of Earth, where it could possibly be captured for analysis of its exterior for dust impacts. If it is recovered, NASA will donate the spacecraft to the Smithsonian Institution for display.

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