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).