Nasa finds missing space probe

The mission team is listening closely for a signal from the unmanned Contour spacecraft, which has been silent since a faulty rocket-firing broke it in two last Thursday.

Scientists say multiple high-powered telescope images confirm that the probe, designed to study comets, is now orbiting the sun about 2.1 million kilometres (1.3 million miles) from Earth.

"The plan is to watch and monitor," said mission director Robert Farquhar in a statement on the Contour web site.

"We realise the possibilities are small, but we can't discount the idea that the spacecraft is still operable. We have to determine that before we give up."

The Contour's mission team says it has trained its antennae on the craft's location to listen for a signal.

After not receiving a command for 96 hours, the craft is programmed to cycle through three of its four antennae to try to send signals automatically.

'Last try'

That procedure takes about 60 hours, meaning that scientists believe the probe, if it can, will call home sometime before 1009 EDT (1509 GMT) on Thursday.

"It may be difficult to hear anything because, depending on the spacecraft's position and condition, the antennae might not have a direct line of sight toward Earth," said mission operations manager Mark Holdridge.

If the mission does not hear anything by Thursday, the craft will be in position to send another signal in December.

"We're obligated to give it this last try," Dr Farquhar said. "And who knows, we might get lucky."

Solar system's origins

The Contour was meant to rendezvous with at least two comets over the next four years on a 48 million km (30 million mile) journey.

By getting within 100 km (60 miles) of Comet Encke in 2003 and Comet Schwassmann-Wachmann 3 in 2006, the spacecraft was supposed to probe the origins of the solar system.

Scientists had hoped that the probe would tell them about the frozen nucleus of each comet, which is believed to be as much as 4.6 billion years old.

The age of the comets' cores means they may hold information about the early stages of the solar system's development.

Nasa says it will look into the malfunction with the Contour mission, which is being run for the space agency by Johns Hopkins University's Applied Physics Laboratory in Laurel, Maryland.

The trouble with the mission is a blow to Nasa, which has also lost two multimillion-dollar unmanned probes to Mars in recent years.