Sakigake and Suisei
Japan's first interplanetary spacecraft, sent to meet Halley's Comet.
Key facts
- Agency
- Institute of Space and Astronautical Science (Japan)
- Type of mission
- Comet flybys
- Target
- Comet 1P/Halley
- Launched
- 7 January and 18 August 1985
- Status
- Completed
Halley's Comet returns to the inner Solar System about every 76 years. For its 1986 visit, space agencies sent a fleet of six spacecraft, later nicknamed the Halley Armada. Japan's contribution was a pair of small probes, its first to leave Earth's neighbourhood.
Two probes
Sakigake, meaning pioneer, was launched on 7 January 1985 as a test craft. It measured the solar wind and magnetic fields and passed Halley on 11 March 1986 at a distance of about 7 million kilometres. Suisei, meaning comet, followed on 18 August 1985 with an ultraviolet camera. It passed Halley on 8 March 1986 at about 151,000 kilometres.
Watching a comet breathe
Suisei imaged the vast cloud of hydrogen around the comet, made when sunlight breaks up water molecules. The brightness of that cloud rose and fell in a regular rhythm, revealing how much water the nucleus released and how that changed as it rotated. Suisei measured the nucleus releasing tens of tonnes of water every second. It was also hit by two dust grains during its flyby, which shows how dusty the space around a comet is.
Why it matters to meteors
The dust that Halley releases spreads along its orbit, and Earth crosses that stream twice a year. The results are two meteor showers, the Eta Aquariids in May and the Orionids in October.
Key dates
| Date | What happened |
|---|---|
| 7 January 1985 | Sakigake launched, Japan's first interplanetary spacecraft. |
| 18 August 1985 | Suisei launched. |
| 8 March 1986 | Suisei passed Halley's Comet at about 151,000 km. |
| 11 March 1986 | Sakigake passed Halley's Comet at about 7 million km. |
See where this mission fits among all the others in the mission timeline.
Did you know?
Halley's Comet will next come close to the Sun in 2061.
The six spacecraft sent to Halley in 1986 came from the Soviet Union, Europe, Japan and the United States.
Related pages
Comets connected with this mission: Halley's Comet. See all comets.