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Mission Profile

Name (pre-launch in parentheses) SUISEI (PLANET-A)
International Designation Code 1985-073A
Objectives Observation of Halley's comet on its approach after 76 years
Launch Date 08:33, August 19, 1985 (JST)
Location Kagoshima Space Center (Uchinoura)
Launch Vehicle
Configuration Weight 140 kg
Shape Cylinder, 1.4m in diameter and 70cm high
Equipped with an 80cm-diameter elliptical high-gain antenna on top of the body

[Click image for enlargement]
Type of Orbit Heliocentric
Period Approx. 282 days
Scientific Instruments
  1. Ultra-Violet Imager (UVI)
  2. Solar wind observation instrument (ESP)
Operation At 14:45 on the launch day, the main responsibility for spacecraft control was relayed from Komaba to Usuda station. For the next 40 days operations included: ranging, automatic sun acquisition, spin control, orbital determination, attitude determination, check and calibration of thrusters, near-quasi normal orbit to ecliptic plane, spin adjustment, check of despun control, check of observational instruments (UVI/ESP), and switch on of high-voltage power. On November 14, orbital adjustment was made aiming at Halley's comet and, on March 8, 1986, SUISEI approached 151,000 km in the side of the Sun away from the comet. After that, SUISEI continued observations of solar wind but, on February 22, 1991, the hydrazine fuel required for orbital change ran out. On August 20, 1992, the final earth swing-by was conducted, completing the mission.
Results As part of the international cooperation program on the exploration of Halley's comet, which had returned after 76 years, SUISEI conducted observations of the comet jointly with VEGAs (former USSR), GIOTTO (Europe) and ICE (U.S.A.). A number of results were acquired including: measurement of rotation period of Halley's comet by ultraviolet imaging; measurement of variations in water-discharge rate; and observation of the scene where ions originating from the comet were captured by the earth magnetosphere. The fleet of six Halley's comet explorers was called the Halley Armada.

List of Halley's Comet Explorers

Explorer Country (Agency) Launch Encounter Closest Distance
VEGA-1 USSR (Intercosmos) December 15, 1984 March 6, 1986 10,000km
VEGA-2 USSR (Intercosmos) December 21, 1984 March 9, 1986 8000km
GIOTTO Europe (ESA) July 2, 1985 March 14, 1986 500km
SAKIGAKE Japan (former ISAS) January 7, 1985 March 11, 1986 7,000,000km
SUISEI Japan (former ISAS) August 18, 1985 March 8, 1986 150,000km
ICE U.S.A. (NASA) August 12, 1978 (Approached comet Giacobini-Zinner in September 1985)