Exploring Comets - Spacecraft Encounters

The first spacecraft encounter with a comet occurred in September 1985, when the International Cometary Explorer (ICE) flew through the tail of Comet Giacobini-Zinner.

The International Sun/Earth Explorer 3 (ISEE-3) satellite, launched in 1978, was designed to monitor the interaction between the solar wind, a stream of charged gas emanating from the Sun, and the Earth's magnetic field. Because of this mission, the spacecraft was not equipped with a camera system, but with numerous instruments to measure the characteristics and composition of the solar wind. When the decision was made to change the trajectory for a comet intercept, the spacecraft was renamed the International Cometary Explorer.

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© Smithsonian.
Photo by Terry McCrea.

A Plasma Wave Detector similar to the one pictured here on display in the National Air and Space Museum is aboard the ICE spacecraft, and measured radio waves produced by ionized gases near Comet Giacobini-Zinner over a period of 24 hours. Gift of Fred Scarf, TRW Space and Technology Group

Comet Halley Missions
Mission	Launch Date	Encounter Date	Distance from Nucleus	Number of Experiments
Vega-1	Dec. 1984	Mar 1986	10,000 km	13
Vega-2	Dec. 1984	Mar 1986	3,000 km	13
Suisei	Aug. 1985	Mar 1986	200,000 km	2
Sakigake	Jan. 1985	Mar 1986	10,000 km	3
Giotto	Jan. 1985	Mar 1986	596 km	10

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The Giotto mission, carrying 10 instruments, came closest to the nucleus of Comet Halley. It flew by the comet 596 kilometers (375 miles) from the nucleus, and returned pictures in visible light, as well as other wavelengths. Giotto was guided in its course by data supplied by the Soviet Vega spacecraft and Earth-based tracking from the US Deep Space Network. See Encounters with Comet Halley for imagery from Giotto.

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The Soviet Vega mission consisted of two identical spacecraft (Vega 1 and Vega 2) launched in December of 1984. Each spacecraft deployed a lander and a balloon at Venus in 1985 and then used a gravity assist at Venus to fly by Comet Halley on March 6, 1986.

Spacecraft orbiting Venus and Earth were used to examine the nucleus and tail of Comet Halley. The International Ultraviolet Explorer (IUE) satellite measured variations in ultraviolet light and found times of brightening that were caused by release of carbon dioxide. Also in Earth orbit, the Solar Maximum Observatory (Solar Max) took pictures of the nucleus in ultraviolet wavelengths.

The Pioneer Venus Orbiter, in orbit around Venus from 1978 to 1992, also provided data on Comet Halley. This spacecraft observed the comet at the time the comet and the Earth were on opposite sides of the Sun, and when the comet was closest to the Sun.

Comet Halley Missions