The Return of Halley's Comet: 1986
On the night of October 16, 1982, the first image of the returning Halley's Comet was recorded with the 200-inch Hale telescope at Palomar Mountain. Caltech astronomers David Jewitt and G. Edward Danielson found the comet when it was still beyond the orbit of Saturn, more than 1.6 billion kilometers (960 million miles) from the Sun.
International Halley Watch
Systematic ground-based observations of 1P/Halley were coordinated by the International Halley Watch. The appearance of comets changes over a short period of time and continuous observations can help record these events. The International Halley Watch network of cooperating observatories and amateur astronomers from more than 40 countries enabled almost continuous recording of images and other data from the comet.
International Halley Watch Reporting Forms were distributed to assist in reporting observations to the International Halley Watch. Standard forms were used by observers in all parts of the world.
Ground-based observers who saw 1P/Halley in 1986 observed its faint long tail streaming away from the Sun.
Rendezvous With Halley's Comet
Five flyby spacecraft representing Earth's scientific community encountered Halley's Comet in early 1986. These vehicles carried instruments which photographed and measured comets, and investigated the solar wind. Although the United States did not launch a spacecraft to investigate Halley's Comet, several experiments by US scientists were aboard the European Space Agency's Giotto and the Soviet Union's Vega spacecraft. Numerous observations were also carried out by spacecraft orbiting Earth and Venus.
Encounters With Halley's Comet
Both the Japanese Suisei (formerly Planet-A) and the European Space Agency's Giotto had imaging systems which sent back the first pictures of the nucleus of a comet. The two Japanese spacecraft were renamed Sakigake (Japanese for "forerunner") and Suisei (Japanese for "comet") after their launches in January and August, 1985. Suisei made its closest approach to Halley's Comet on March 8, 1986, when it passed 151,000 kilometers (95,000 miles) from the nucleus. The Russian Vega spacecraft also imaged Halley's Comet in 1986, but at a much lower resolution.
In contrast to the long tail seen from Earth, jets of gas pointing towards the Sun were photographed by the Giotto spacecraft on March 13, 1986. The nucleus of Halley's Comet is 15 kilometers (9 miles) long by 8 kilometers (5 miles) wide.