September 2, 2008
Rosetta To Fly By Steins Soon
The Rosetta spacecraft control room is buzzing with anticipation as Rosetta closes in on asteroid 2867 Steins. The fly-by timeline includes a series of critical events, culminating with closest approach - expected at 20:58 CEST, 5 September 2008.
At the time of closest approach, Rosetta is planned to be 800 km from the asteroid, passing by at a speed of 8.6 km/s relative to Steins. Both Rosetta and Steins will be illuminated by the Sun, providing an excellent opportunity for science observations.Between 40 and 20 minutes before closest approach, Rosetta will be flipped and the spacecraft will switch to a specially designed asteroid fly-by mode, an optimal configuration that supports the intensive observation and tracking activity of the on-board instruments.
Although most scientific observations will take place in the few hours around closest approach, several instruments will be switched on for a longer time around the event.
ESA's Cebreros deep space antenna (DSA 2) in Cebreros, Spain, will be used for communications with Rosetta in the two days preceding closest approach. When the spacecraft is not visible from Cebreros or New Norcia, NASA's DSN (Deep Space Network) ground stations at Goldstone, Canberra and Madrid will provide support for tracking and for science operations.
Around closest approach, Rosetta will be 2.41 Astronomical Units, or about 360 million km, from Earth. Radio signals sent to and from the spacecraft will have a 20 minute one-way travel time.
Image 1: This diagram shows the approach of Rosetta's spacecraft to asteroid (2867) Steins on 5 September 2008. Steins is located in the main asteroid belt between the orbits of Mars and Jupiter. The encounter took place during Rosetta's first incursion into the main asteroid belt while on its way to Comet 67P/Churyumov-Gerasimenko. Credits: ESA, image by C.Carreau
Image 2: ESA's Rosetta spacecraft flew by asteroid (2867) Steins on 5 September 2008 at 20:58 CEST, ground received time (= spacecraft time CEST + 20 minutes), with a closest approach distance of 800 km. Steins is Rosetta's first nominal scientific target. The spacecraft encountered the asteroid in the course of its first incursion into the main asteroid belt located between the orbits of Mars and Jupiter, while on its way to Comet 67P/Churyumov-Gerasimenko. The study of asteroids is extremely important because they represent a sample of Solar System material at different stages of evolution "“ key to understanding the origin of our own planet and of our planetary neighborhood. Credits: ESA, image by C.Carreau
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