Members of the private, California-based Planetary Society said on Wednesday that the Cosmos 1 was likely lost less than two minutes after takeoff on Tuesday.
But they said the spacecraft might have freed itself from the failing Russian booster rocket and orbited long enough to send weak signals that were apparently received by three ground stations within hours of its launch.
"We all here rate it as a 1% probability, but stranger things have happened and spacecraft have been found in unplanned orbits, so we are still hoping," Planetary Society executive director Louis Friedman said from Moscow.
Mission controllers have asked US Strategic Command and other tracking stations to continue scanning the skies for the missing spacecraft and said they planned to keep sending commands to see if Cosmos 1 responds.
Cosmos 1 was launched on Tuesday from a submerged Russian submarine in the Barents Sea in the tip of a converted intercontinental ballistic missile. But the disc-shaped craft lost contact with its controllers almost immediately.
"We all here rate it as a 1% probability, but stranger things have happened and spacecraft have been found in unplanned orbits, so we are still hoping"
Planetary Society executive director Louis Friedman
The Russian Space Agency said the Volna rocket's first stage misfired within 83 seconds of liftoff.
The failure is the second involving the Cosmos 1 mission. A 2001 test deployment of its 15-metre sail panels was spoiled because of problems with the Russian rocket.
Planetary Society officials maintained all along that the $4-million mission, run by volunteers out of a 1920s bungalow in Pasadena, California, would be risky but hoped it would spur public interest in a race to the stars aboard sunlight-propelled spacecraft.
"We have no regrets over what's happened," said Bruce Murray, Planetary Society chairman. "We learned a lot and I think we have shown what can be possible and what might be able to be done."
Cosmos 1 was to have unfurled a 30-metre petal-shaped solar sail to power its planned orbit around Earth. Streams of photons, or light particles, from the sun would strike the ultra-thin Mylar sail and propel the craft forward in the vacuum of space at ever-increasing speeds.
Friedman said the society would continue to back solar sail technology with its own mission or by helping other teams.
It has an agreement to share data from the Cosmos 1 mission with Nasa, which is testing solar sail spacecraft propulsion systems at its own research centre.
US space agency Nasa says the
solar sail technology is viable
Les Johnson, manager of the Space Propulsion Technology Project at Nasa's Marshall Space Flight Centre in Alabama, said the technology was viable and could be ready to launch on a science mission within a couple of years.
"We are excited because it's a technology we need," Johnson said. "Solar sails are going to let us do things we currently can't do in space."