NASA's old and injured Deep Space 1 probe is set for a comet fly-by on Saturday, only the second ever attempt to take close-up snaps. But scientists working on the mission say the probe could be destroyed before it sends any pictures back.
"We expect to be hit by debris from the comet," says Marc Rayman, project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "Even a tiny particle might prove fatal."
The probe was launched in 1998 to test experimental systems including an ion thruster and artificial intelligence software. With the tests complete, Rayman's team decided to extend the probe's mission and sent it off on course to intercept a nearby comet called Borrelly. The comet is currently 200 million kilometres from the Sun, the closest it will get for another seven years.
The probe will fly to within 2000 kilometres of the comet's nucleus, passing through a 50,000 kilometre wide ball of gas and dust that surrounds the hard centre. Using a camera and infra-red spectrometer, scientists hope to grab images of gas being ejected from the comet and analyse compounds shed from the surface.
"It'll help us to nail down the mineralogy of the surface and find out how the gas and dust are ejected," says Jürgen Oberst of the German Aerospace Research Establishment in Berlin, who is working with Rayman.
To be successful, the probe will have to avoid, or survive, impact with particles travelling at over 16 kilometres a second. "The flyby is risky," says Oberst. "And it has to get through to the other side and turn around and transmit the images and data back. We'll be really lucky if we get good data," he says. If this happens, the data and images will be sent on Sunday.
Four other missions are planned to rendezvous with comets in the future: Rosetta, Deep Impact, Contour and Stardust.
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