NASA prepares to view comet close up

Oct 27, 2010, 2:40 GMT

Washington - Astronomers are preparing for an up-close and personal look next week at a comet, which they say will provide the best extended view yet at that class of objects in the solar system.

The Deep Impact spacecraft will pass within 700 kilometres of comet Hartley 2 at a speed of 43,000 kilometres per hour on November 4. Its mission, dubbed Epoxi, is to take high resolution images of the comet's nucleus using two telescopes with digital and an infrared spectrometer.

Scientists have captured close images of four other comets, but never one with such a small nucleus, and hope Hartley 2 will provide new details about the composition of comets and the formation of the solar system.

Deep Impact is being reassigned after delivering a probe to crash into the comet Tempel 1 in 2005, in the first such look at the inner material of a comet. The mother ship, however, remained in good condition, and NASA decided to repurpose the spacecraft for a look at another comet.

Hartley 2 is much smaller - with a nucleus that is about a kilometre wide - and more visible from Earth than Tempel 1, providing scientists a chance to compare the celestial objects. They also hope to learn about jets of material emitted by comets.

The orbiting bodies of ice, dust and gas are considered key to learning about the formation of the solar system, because they are believed to be leftover building blocks of the early solar system that may have brought water and other organic compounds to Earth.

The craft will send back 64,000 pictures with its camera, which is fine tuned enough to 'distinguish between a car and a pickup truck' from 640 kilometres away, said Amy Walsh, lead engineer of the mission. Deep Impact has already been sending back images as it nears Hartley 2 and will continue to do so even after passing close by the comet, collecting a total of 11 weeks of data.

The comet was discovered by Australian astronomer Malcolm Hartley in 1986 during a survey of the southern sky.