ESA’s Rosetta spacecraft is on its way to a rendezvous with a comet in 2014. During its 10-year trek through deep space, Rosetta will make two visits to the main asteroid belt, between Mars and Jupiter. Its first historic encounter with an asteroid will take place at 20:58 CEST (Central European Summer Time) on 5 September.
Since its launch in March 2004, Rosetta has travelled about 3,700 million km. It is currently more than twice Earth’s distance from the Sun. The spacecraft has already swept past the Earth (twice) and Mars, but its flyby of the small, rocky asteroid named Steins offers the first real opportunity to use its scientific instruments.
Rosetta will zoom past Steins at a speed of about 31,000 km per hour. Since early August, images taken by its cameras have been used to track Steins and pinpoint its position. This will enable the spacecraft to pass only 800 km from its target. Unfortunately, controllers at ESA’s European Space Operations Centre in Darmstadt, Germany, will have to wait until 22:23 CEST for first contact with Rosetta and confirmation of a successful flyby.
Steins was discovered in 1969 and measures only a few kilometres across. Regular changes in its brightness show that it spins roughly once every 6 hours. Scientists are keen to learn more about this little world because it is a relatively rare type of asteroid. Objects such as Steins are left-overs from the birth of the planets, 4.5 billion years ago. By studying them, we can learn more about the formation of Earth and the other planets in the Solar System.
