The privately funded Cosmos-1 craft was launched overnight on a Russian missile from a submarine in the Barents Sea.

The Russian Navy began a search for wreckage after launch data suggested the rocket booster failed.

But the US team also working on the project reported that a weak signal from the craft had been detected.

Note of caution

According to the website for the California-based Planetary Society, which sponsored the craft, signals were recorded independently at three ground stations, at Petropavlovsk in Kamchatka, Majuro in the Marshall Islands and Panska Ves in the Czech Republic, that Cosmos-1 was expected to pass over.

But Jiri Simunek, a scientist at Panska Ves, told the BBC News website that no signal had been detected by the Czech tracking station, "just noise".

"The booster's failure means that the solar sail vehicle was lost," said agency spokesperson Vyacheslav Davidenko.

"The Russian navy is searching the area for the debris of the booster and the vehicle."

A satellite monitoring the launch also failed to detect a signal from Cosmos-1.

Project director Dr Louis Friedman warned that it was still too early to determine whether the signals recorded at ground stations definitely came from Cosmos-1. He suggested the craft could have made it into orbit, but a lower one than expected.

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"That the weak signals were recorded at the expected times of spacecraft passes over the ground stations is encouraging, but in no way are they conclusive enough for us to be sure that they came from Cosmos-1 working in orbit," Dr Friedman said.

"I think we'll just have to be patient and let some more analysis be done for maybe even several days," he told the BBC.

But he added that even if Cosmos-1 did survive the launch, a low orbit meant it was likely to re-enter the atmosphere and burn up.

Rocket failure

The Russian-built Cosmos-1 was launched aboard a modified Volna intercontinental ballistic missile (ICBM) from the nuclear submarine Borisoglebsk.

The sail reflects particles of light, or photons, from the Sun, gaining momentum in the opposite direction.

Some think solar sails offer a cheaper, faster form of spacecraft propulsion.

"Solar sailing is really the only known technology that could potentially take us to the stars one day because it does not have to carry fuel with it and because it can keep accelerating - even at incredible distances," the Planetary Society's Amir Alexander told the BBC.

The acceleration from sunlight is very small; but the advantage of solar sailing over chemical propulsion is that the acceleration is sustained.

If successful Cosmos-1 will get faster and faster - and climb higher in orbit - as time goes on.

The 100kg (220lbs) craft had been scheduled to reach an 800km- (500 mile-) high orbit.

It would then take pictures of Earth for four days before unfurling its eight aluminium-backed plastic sail blades into a 30m (100ft) circle.

The US, European, Japanese and Russian space agencies also have solar sail programmes in the offing.