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Suisei

An artist's rendering of the Suisei spacecraft
Names	PLANET-A
Mission type	Halley flyby
Operator	ISAS
COSPAR ID	1985-073A
SATCAT no.	15967
Website	isas.ac.jp
Mission duration	5 years, 6 months and 4 days
Spacecraft properties
Launch mass	139.5 kg (308 lb)
Start of mission
Launch date	August 18, 1985 23:33 UTC
Rocket	M-3SII
Launch site	Uchinoura Space Center
End of mission
Disposal	Decommissioned
Deactivated	February 22, 1991
Orbital parameters
Reference system	Heliocentric
Flyby of 1P/Halley
Closest approach	March 8, 1986
Distance	151,000 km (94,000 mi)
Flyby of Earth
Closest approach	August 20, 1992
Distance	~900,000 km (560,000 mi)
PLANET seriesNozomi → Halley Armada← Giotto

Suisei (すいせい, lit. "Comet"), originally known as Planet-A, was an uncrewed space probe developed by the Institute of Space and Astronautical Science (now part of the Japanese Aerospace Exploration Agency, or JAXA).

It constituted a part of the Halley Armada together with Sakigake, the Soviet Vega probes, the ESA Giotto and the NASA International Cometary Explorer, to explore Halley's Comet during its 1986 sojourn through the inner Solar System.

Spacecraft

Suisei was identical in construction and shape to Sakigake, but carried a different payload: a CCD UV imaging system and a solar wind instrument.

The main objective of the mission was to take UV images of the hydrogen corona for about 30 days before and after Comet Halley's descending crossing of the ecliptic plane. Solar wind parameters were measured for a much longer time period.

The spacecraft is spin-stabilized at two different rates (5 and 0.2 rpm). Hydrazine thrusters are used for attitude and velocity control; star and Sun sensors are for attitude control; and a mechanically despun off-set parabolic dish is used for long range communication.

Launch

Suisei was launched on August 18, 1985 by M-3SII launch vehicle from Kagoshima Space Center on M-3SII-2 mission. It was sent on an intercept course with Comet Halley, after which it would remain in a heliocentric orbit for later use as long as it was viable.

Halley encounter

Suisei began UV observations in November 1985, generating up to six images/day.

The spacecraft encountered Comet Halley at 151,000 km on sunward side during March 8, 1986, suffering only two dust impacts.

Earth flyby

Fifteen burns of Suisei's 3 N motors during the period of April 5–10, 1987, yielded a 65 m/s velocity increase for a 60,000 km Earth gravity assist swingby on August 20, 1992, although the craft was then lost behind the Sun for the summer.

The hydrazine fuel was depleted on February 22, 1991. Preliminary tracking indicated a 900,000-km flyby had been achieved.

Other planned encounters

ISAS had decided during 1987 to guide Suisei to a November 24, 1998, encounter with 21P/Giacobini-Zinner, but due to depletion of the hydrazine, this, as well as plans to fly within several million kilometers of Comet 55P/Tempel-Tuttle on February 28, 1998, were cancelled.

References

1. "Suisei". NASA Space Science Data Coordinated Archive. Retrieved December 2, 2022.

External links

• Suisei
• Suisei Mission Profile by NASA's Solar System Exploration
• Halley's Comet Flyby
• Suisei Mission Comet Halley Data Archive at the NASA Planetary Data System, Small Bodies Node

v t e Spacecraft missions to minor planets and comets
List of minor planets and comets visited by spacecraft List of artificial objects on extraterrestrial surfaces
Active	New Horizons (multiple flybys) OSIRIS-APEX (orbiter) Hayabusa2♯ (lander) Lucy (multiple flybys) Psyche (orbiter) Hera (orbiter) AIDA
Past	Flybys Cassini–Huygens Chang'e 2 Clementine CONTOUR Deep Impact EPOXI Deep Space 1 Galileo Halley Armada Giotto Sakigake Suisei Vega 1 Vega 2 International Cometary Explorer LICIACube NEA Scout NEAR Shoemaker Pioneer 7 PROCYON Rosetta Stardust Ulysses Orbiters Dawn NEAR Shoemaker Rosetta Timeline Landers Hayabusa MINERVA Hayabusa2 MASCOT Rover-1A / HIBOU Rover-1B / OWL Rover-2 NEAR Shoemaker Philae Impactors Deep Impact DART AIDA Sample return Hayabusa Hayabusa2 Stardust OSIRIS-REx
Planned	Tianwen-2 (multiple flybys and sample return, 2025) DESTINY+ (multiple flybys, 2028) MBR Explorer (multiple flybys and orbiter, 2028) Comet Interceptor (flyby, 2029)
Proposed	Shensuo (flybys, 2024) ASTER (orbiter, 2025) Ramses (2029) Interstellar Probe (flyby, 2030–2042)
Cancelled or not developed	AGORA AIM Asteroid Redirect Mission Athena CAESAR Castalia Centaurus Chimera Clementine 2 Comet Hopper CONDOR CORSAIR CRAF Don Quijote HAMMER Hayabusa Mk2 Janus MAOSEP MANTIS Marco Polo New Horizons 2 OKEANOS Vesta
Related	Asteroid belt Asteroid capture Asteroid mining Colonization of asteroids Ceres Pluto Exploration Small Solar System bodies Near-Earth object Trans-Neptunian object Colonization Trojan Vesta
Probes are listed in chronological order of launch. indicates mission failures.

• Japanese space probes
• Missions to Halley's Comet
• Satellites orbiting the Sun
• 1985 in spaceflight
• Derelict space probes
• Spacecraft launched in 1985
• Japanese inventions