2008-09-08 - Rosetta Steins flybyRosetta observes asteroid Steins at close quarters
Kometensonde fliegt in 800 km an Steins vorbei<br /> On 5 September, ESA's comet chaser, Rosetta, flew by a small body in the main asteroid belt, asteroid Steins, collecting a wealth of information about this rare type of minor Solar System body. At 20:58 CEST (18:58 UT) ESA's Rosetta probe approached asteroid 2867 Steins, coming to within a distance of only 800 km from it.
Steins is Rosetta's first nominal scientific target in its 11 and half year mission to ultimately explore the nucleus of Comet 67P/Churyumov-Gerasimenko.
The success of this 'close' encounter was confirmed at 22:14 CEST, when ESA's ground control team at the European Space Operations Centre (ESOC) in Darmstadt, Germany, received initial telemetry from the spacecraft. During the flyby operations, Rosetta was out of reach as regards communication links because its antenna had to be turned away from Earth. At a distance of about 2.41 AU (360 million kilometres) from our planet, the radio signal from the probe took 20 minutes to reach the ground.
Steins is a small asteroid of irregular shape with a diameter of only 4.6 km. It belongs to the rare class of E-type asteroids, which had not been directly observed by an interplanetary spacecraft before. Such asteroids are quite small in size and orbit and are mostly found in the inner part of the main asteroid belt located between Mars and Jupiter. They probably originate from the mantle of larger asteroids destroyed in the early history of the Solar System, and are thought to be composed mainly of silicate minerals with little or no iron content.