Washington

Out with a bang: NASA's comet-seeking craft CONTOUR may have met a premature end. Credit: NASA

Comet research in the United States is facing an uncertain future after mission managers all but gave up hope of salvaging the CONTOUR (Comet Nucleus Tour) spacecraft. The craft went silent on 15 August as it fired an onboard rocket to leave Earth orbit.

The NASA-funded spacecraft was built and operated by the Johns Hopkins University Applied Physics Laboratory (APL) near Baltimore, Maryland. It was supposed to have visited two comets in four years, beginning with Comet Encke in 2003, to take close-up photographs of their icy nuclei (see Nature 417, 889; 200210.1038/417889a). Now the $159-million mission seems to be a total loss.

For US comet investigators, CONTOUR's demise is the latest and most calamitous in a long line of setbacks. The United States was the only major spacefaring nation not to send a craft to Halley's Comet in 1986, and several NASA comet projects have been cancelled since, including the Comet Rendezvous Asteroid Flyby a decade ago, and a US lander for Europe's Rosetta mission, which is expected to rendezvous with a comet in 2011.

CONTOUR had operated flawlessly in the weeks after its 3 July launch, circling Earth as its orbit shifted gradually into the proper alignment to head towards Encke. This 'indirect launch mode' technique, pioneered on this mission, was designed partly to allow the use of a cheaper launch vehicle. Once the orbit was aligned, an onboard rocket motor fired to boost CONTOUR into interplanetary space.

Ground controllers had expected to establish radio contact with the spacecraft shortly after the engine fired, but they never received a signal. Then, one day after CONTOUR vanished, the Spacewatch asteroid-tracking telescope in Arizona photographed two small objects streaking away from Earth at a distance of about 460,000 kilometres, in roughly the position CONTOUR would be if the rocket had fired. Mission managers took this as evidence that the spacecraft had broken into two pieces after the rocket fired, or that some part had come detached.

With no telemetry data or additional pictures, it will be difficult to determine what happened to CONTOUR. Although radio and optical telescopes continued searching the sky, APL managers were not optimistic about regaining contact as of early this week.

Mission director Robert Farquhar of APL was non-committal about whether his team might repropose the mission to NASA. CONTOUR was funded under the agency's Discovery programme for planetary exploration, and its price tag was only half the typical cost of such a mission. But other cometary spacecraft are being prepared for launch in the next few years, and it would take the CONTOUR team at least that long to ready a replacement.

For Farquhar, CONTOUR's loss was especially frustrating. “I wrote my first paper on getting to Encke's comet in 1972,” he told the press last week. “I've been at this for 30 years, so I would like to have gotten some images.”