Suisei
Other Name(s)
National Affiliation: Japan
Launch Date/Time: 1985-08-18 at 23:33:00 UTC
Launch Vehicle: M-3SII
On-orbit dry mass: 139.50 kg
Nominal Power Output: 100.00 W
Description
Suisei (the Japanese name meaning `Comet') was launched on March 18, 1985
into heliocentric orbit to fly by Comet P/Halley. It is identical to
Sakigake apart from its 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. Suisei began UV observations in Nov. 1985, generating
up to 6 images/day. The spacecraft encountered Comet P/Halley at 151,000 km
on sunward side during March 8, 1986, suffering only 2 dust impacts.
Fifteen burns of Suisei's 3 N motors over 5--10th of April 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 was depleted on 22 February 1991. Preliminary
tracking indicated a 900,000 km flyby had been achieved.
ISAS had decided during 1987 to guide Suisei to
a Nov. 24, 1998 encounter with P/Giacobini-Zinner, but due to
depletion of the hydrazine, this, as well as plans to
fly within several million kilometers of
Comet P/Tempel-Tuttle on Feb. 28, 1998 has been cancelled.
