Asteroid Steins belongs to the rare, largely unknown intermediate E-class, very bright and probably with a much-weathered surface. Steins' orbit was only known from ground observations, so Rosetta is conducting Europe's first-ever optical tracking campaign, providing highly accurate position data to Flight Dynamics specialists who are planning a series of trajectory corrections for an accurate fly-by. For over a year, Rosetta scientists and leading asteroid experts have been planning this encounter, and all the probe's science instruments will be active at some point in the fly-by. Reception of the first images is expected at the European Space Operations Centre some two hours after the encounter on 5 September 2008.

ESApod video programme