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, originally known as Planet-A, was an unmanned
space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; o ...
developed by the
Institute of Space and Astronautical Science (ISAS) is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan's space development. Since 2003, it is a division of Japan Aerospace E ...
(now part of the Japanese Aerospace Exploration Agency, or JAXA). It constituted a part of the
Halley Armada The Halley Armada is the name of a series of space probes, five of which were successful, sent to examine Halley's Comet during its 1986 sojourn through the inner Solar System, connected with apparition "1P/1982 U1". The armada included one prob ...
together with ''
Sakigake , known before launch as MS-T5, was Japan's first interplanetary spacecraft, and the first deep space probe to be launched by any country other than the USA or the Soviet Union. It aimed to demonstrate the performance of the new launch vehi ...
'', the
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, a ...
probes, the ESA ''Giotto'' and the
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
International Cometary Explorer The International Cometary Explorer (ICE) spacecraft (designed and launched as the International Sun-Earth Explorer-3 (ISEE-3) satellite), was launched 12 August 1978, into a heliocentric orbit. It was one of three spacecraft, along with the mo ...
, to explore
Halley's Comet Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the on ...
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 The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
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 A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...
is spin-stabilized at two different rates (5 and 0.2 rpm).
Hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
thrusters are used for attitude and velocity control;
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
and sun sensors are for attitude control; and a mechanically despun off-set parabolic dish is used for long range
communication Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inqui ...
.


Launch

''Suisei'' was launched on August 18, 1985 by
M-3SII The Mu, also known as M, was a series of Japanese solid-fueled carrier rockets, which were launched from Uchinoura between 1966 and 2006. Originally developed by Japan's Institute of Space and Astronautical Science, Mu rockets were later operate ...
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 A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...
for later use as long as it was viable.


Halley encounter

''Suisei'' began UV observations in November 1985, generating up to 6 images/day. The spacecraft encountered Comet Halley at 151,000 km on sunward side during March 8, 1986, suffering only 2 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 Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
gravity assist In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...
swingby on August 20, 1992, although the craft was then lost behind the Sun for the
summer Summer is the hottest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, the earliest sunrise and latest sunset occurs, daylight hours are longest and dark hours are shortest, wit ...
. The
hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, 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


External links


''Suisei''

''Suisei'' Mission Profile
b
NASA's Solar System Exploration



''Suisei'' Mission Comet Halley Data Archive
at the NASA Planetary Data System, Small Bodies Node {{DEFAULTSORT:Suisei (Probe) Japanese space probes Missions to Halley's Comet Satellites orbiting the Sun 1985 in spaceflight Derelict space probes Spacecraft launched in 1985 Japanese inventions