European Comet Probe Swings Past Asteroid
Illustration of asteroid with Rosetta approaching in the distance.
Credit: ESA/AOES Medialab

A European spacecraft zoomed by a rocky asteroid Friday in the first of two pit stops on the way to a distant comet.

The European Space Agency?s (ESA) Rosetta comet probe zipped by the asteroid Steins, a space rock in the asteroid belt between the planets Mars and Jupiter, as it streaked across the solar system millions of miles from Earth.

Rosetta made its closest pass by Steins, officially known as Asteroid 2867, at 2:58 p.m. EDT (1858 GMT), and swung within 500 miles (800 km) as it flew past at a clip of 19,262 mph (31,000 kph).

The probe has had Steins in its sights for weeks, and was expected to train its 11 instruments onto the space rock and begin beaming the first images back to ESA?s mission control center in Darmstadt, Germany later tonight.

Mission managers received their first post-flyby signal from Rosetta at about 4:14 p.m. EDT (2014 GMT). Images of the event showed mission controllers celebrating with wide smiles and hugs.

?The entire Flight Control Team just let out a loud cheer!? wrote Daniel Scuka, an ESA writer chronicling Rosetta?s flyby on the ESA mission?s blog.

Launched in March 2004, Rosetta and its lander Philae are headed for a planned 2014 rendezvous with the comet 67/P Churyumov-Gerasimenko. Friday?s encounter with Steins and a second flyby past the asteroid Lutetia in 2010 are expected to serve as dry runs for Rosetta?s comet encounter and shed new light on the composition and orbits of similar space rocks.

Aside from some minor challenges, the flyby appeared to go well.

?The status of the spacecraft is nominal,? said Andrea Accomazzo, spacecraft operations manager for Rosetta, in an ESA interview before the probe made its closest approach. ?We had some issues in finding the proper setting of the cameras to do the tracking but now we?ve configured all the parameters and we?re very satisfied with the tracking that we?re receiving.?

Astronomers believe Steins is a Class E-type asteroid, one of the rarest kinds of space rocks in the solar system, and may hold in its rocky interior clues to how planets and other objects formed billions of years ago, ESA officials have said. The asteroid may actually have been part of an even larger space rock that chipped off in the distant past, they added.

The space rock is relatively small, about 3.1 miles (5 km) wide, and circles the sun from a distance of about 219 million miles (353 million km).

Rosetta?s Steins flyby is the latest in a series of space rendezvous for the probe as it makes its way out toward the comet 67/P Churyumov-Gerasimenko.

The spacecraft flew past Earth twice, in March 2005 and November 2007, respectively, with a third pass by the planet due in November 2009. The spacecraft also flew past the planet Mars in February 2007 and is slated to rendezvous with the asteroid Lutetia in June 2010 before heading off to its cometary quarry.

Today?s asteroid flyby marked the first of two very different space milestones for ESA officials.

While scientists and engineers monitored Rosetta?s rendezvous from their control center in Darmstadt, Germany, another team at a control center in Toulouse, France geared up for the planned 5:30 p.m. EDT (2130 GMT) undocking of the cargo ship Jules Verne - Europe?s first Automated Transfer Vehicle? - from the International Space Station.

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