Controllers of the experimental LightSail spacecraft say they have re-established contact with it and successfully deployed its solar sail after a previous attempt had failed.
Two days after its launch May 20, the spacecraft's handlers at the non-profit nonprofit Planetary Society and its university partners lost contact when the LightSail took itself offline after experiencing a software glitch.
Mission manages said the glitch put its solar-powered batteries in a "sleep" or safe mode, possibly as result of the solar cells experiencing a "ping-pong" effect of first too much and then too little sunlight.
After 8 days of silence the craft rebooted itself, but then went silent again last week.
Controllers managed to reestablish contact June 6 and, after a first failed attempt, managed to activate the tiny motor that began to unfurl the 344-square-foot thin Mylar sail.
"All indications are that the solar sail deployment was proceeding nominally," mission manager David Spencer wrote on the Planetary Society blog.
The late astronomer Carl Sagan first proposed the concept of a spacecraft that can propel itself through space using the pressure of sunlight on a thin, giant sail in the 1970s.
Sagan founded the Planetary Society, which is now headed by Bill Nye, known best as television educator "Bill Nye the Science Guy," who tweeted about the sail deployment.
"Motor is running! Sail is Deploying!!! 39 Years after Prof. Sagan spoke of it!"
-Bill Nye (@BillNye) June 7, 2015
Motor is running! Sail is Deploying!!! 39 Years after Prof. Sagan spoke of it!
— Bill Nye (@BillNye) June 7, 2015
The society promotes itself at the largest private space-advocacy organization.
The LightSail is a proof-of-concept project, with a goal of demonstrating successful sail deployment.
It is in too low an orbit to do much actual solar sailing, controllers said, but the society has announced plans for another LightSail mission next year in which a spacecraft will be put in higher orbit to test the concept of "surfing" on the sun's light rays.
The Planetary Society has launched a Kickstarter campaign to fund a second mission, which has so far raised more than $800,000.
"We've learned a lot about perseverance on this test mission," Nye said in a society release. "Although it's in inertial space, LightSail has had me on a rollercoaster. We are advancing space science and exploration. This mission is part of our mission."
The society has encouraged amateur astronomers to participate in the mission by attempting to observe the spacecraft passing overhead, and is posting its constantly updated estimated position, along with information for radio trackers, on its mission control page.