Deep Space 1
The spacecraft that proved ion engines in deep space, then flew past a comet.
Key facts
- Agency
- NASA (United States)
- Type of mission
- Technology test, asteroid and comet flybys
- Target
- Asteroid 9969 Braille and comet 19P/Borrelly
- Launched
- 24 October 1998
- Status
- Ended 2001
Deep Space 1 was built to test new technology so that later missions would not have to take the risk. It flew twelve new systems, including a navigation system that steered the craft by itself using pictures of asteroids against the stars.
The ion engine
Its most important test was an ion engine: an electric thruster that uses solar power to accelerate charged xenon atoms out of the back at very high speed. The push is tiny, about the weight of a sheet of paper, but it can run for months and uses very little fuel. Deep Space 1 ran its engine for more than 16,000 hours. Dawn, Hayabusa, Hayabusa2 and Psyche all owe their journeys to electric propulsion proven on this mission.
Braille and Borrelly
In July 1999 it flew past the small asteroid Braille, whose colours resemble the basaltic HED meteorites from Vesta. Then, after its star-tracking camera failed and engineers reprogrammed it to navigate with its science camera instead, it flew past comet 19P/Borrelly on 22 September 2001 at about 2,200 kilometres.
Borrelly's nucleus is about 8 kilometres long and shaped a little like a bowling pin. It is extremely dark, and its surface proved dry and hot, with the comet's gas and dust escaping from a few active areas. It was the clearest view of a comet nucleus since Giotto.
Why it matters to meteorites
The dark, dry crust of Borrelly suggested that much of a comet's surface is a layer of dust and organic matter left behind as ice escapes, a link to the darkest primitive meteorites.
Key dates
| Date | What happened |
|---|---|
| 24 October 1998 | Deep Space 1 launched on a Delta II rocket. |
| 29 July 1999 | Flew past the asteroid 9969 Braille. |
| 22 September 2001 | Flew past comet 19P/Borrelly at about 2,200 km. |
| 18 December 2001 | The ion engine was switched off and the mission ended. |
See where this mission fits among all the others in the mission timeline.
Did you know?
The asteroid Braille is named after Louis Braille, who invented the reading system for blind people.
Deep Space 1's ion engine was about ten times as efficient with its fuel as a chemical rocket.
Related pages
Comets connected with this mission: Comet Borrelly. See all comets.