Artist's impression of asteroid Steins from the perspective of the spacecraft.
Artist's impression of asteroid Steins from the perspective of the spacecraft
The Rosetta spacecraft flew by asteroid Steins in September 2008. Closest approach was on 5 September 2008 at 18:38 UTC at which time the spacecraft was about 800 km from the asteroid. The relative speed was 8.6 km/s.
The planned fly-by strategy allowed for continuous observation of the asteroid before, during and after closest approach and was optimised for low closest approach and for a large phase angle coverage (from 0 to 140 degrees).