One of our space probes is missing, Nasa admits after mission goes awry

A space probe designed to rendezvous with a comet has gone missing after scientists at Nasa tried to send it into a new trajectory.

Engineers lost radio contact with the £100m Contour spacecraft after transmitting signals that should have fired its rocket to fling the probe out of its Earth orbit.

Robert Farquhar, the Contour mission director at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said Nasa was now trying to locate the probe through its Deep Space Network of radio telescopes.

Nasa is also sending radio signals to the probe in the hope it might trigger a response which will enable the engineers to regain contact and take control of the solar-powered spacecraft. "We're still trying to get a telemetry link. We're trying to send commands to the spacecraft to switch between its two transmitters and use different on-board antennas, in case they are turned off for some reason," Dr Farquhar said yesterday.

One possibility is that one of Contour's antennae has been knocked during the rocket propulsion. Another is that an explosion has destroyed the spacecraft entirely. "But we really won't know what happened until we contact it," he said.

Contour's rocket motor is fuelled with solid propellent and was programmed to ignite on Thursday morning to redirect the space probe out of its orbit and along a path that would send it past two comets.

However, the scheduled "burn" took place about 140 miles above the Indian Ocean when the probe was too low on the Earth's horizon to be detected by the Deep Space Network. Engineers failed to regain contact at the expected time after the burn and when no signal was received the team immediately began working through its back-up plans to re-establish contact.

The Deep Space Network's radio telescopes are being trained on the trajectory the space probe should have taken if its rocket had fired as expected. "We're looking at the nominal path as if the burn occurred. We're working on the assumption that the motor fired, and the team is putting its priority there," Dr Farquhar said.

Dr Farquhar said that without knowing what had happened to Contour it was difficult to know what commands it could execute. But the scientists are "cautiously optimistic" they will find it.