LightSail Back on Track for Solar Sail Deployment

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Editor’s Note: The Planetary Society’s LightSail spacecraft has gone silent again. The spacecraft failed to communicate on any of a series of passes over ground stations Thursday (June 4), a day after it extended its solar arrays. Engineers suspect a battery problem of some kind put the spacecraft into a power-conserving safe mode. Controllers had planned to deploy the spacecraft’s solar sail Friday (June 5) prior to the battery problem

WASHINGTON — After worrisome computer glitches and a miraculous cosmic reboot, the Planetary Society is fairly sure its LightSail test spacecraft successfully raised its side-mounted solar panels Wednesday (June 3), literally clearing the way for deploying the cubesat’s 32-square-meter solar sail Friday. 

Jason Davis, a spokesman for the Pasadena, California-based Planetary Society, said late Wednesday night that LightSail’s onboard cameras weren’t able to provide visual confirmation that the craft’s hinged side panels opened, but temperature readings from the panel’s solar cells dropped to -48 Celsius, indicating that the panels were open and no longer in direct sunlight. LightSail’s sensors also showed an increase in angle of the sun relative to the panels and that the craft’s rotational rate had changed. These are also signs of success.

Two days after a successful May 20 launch to orbit aboard the U.S. Air Force’s X-37B spaceplane, LightSail encountered a software glitch that caused the craft to cease transmitting data and go silent. On May 31 ground stations reestablished contact with the spacecraft.  A random cosmic ray had hit the LightSail and caused the computer reboot, which was just what the team needed to fix the satellite.

But LightSail isn’t out of the woods yet. After deploying the panels, the craft reported abnormally low voltages to ground stations.

“With battery levels continuing to hover around 3.9 volts during subsequent ground passes, the team postponed image acquisition to focus on stabilizing the spacecraft,” Davis said. “Ideally, the batteries should be topped off at 4.2 volts before proceeding with power-intensive activities, including sail deployment.”

“Providing battery levels return to normal, and any outstanding issues are resolved, a Friday deployment could still be in the works,” he said.

When the LightSail project began in 2009, San Luis Obispo, California-based Stellar Exploration, Inc. was in charge of building the craft. But in 2014 Ecliptic Enterprises Corp. took over the integration and testing of LightSail, working out of Cal Poly San Luis Obispo. Borealis Space also worked on LightSail as a subcontractor to Ecliptic.

The project is crowdfunded on Kickstarter with the help of the Planetary Society’s chief executive, Bill Nye, who is known to millions thanks to his long-running television show “Bill Nye the Science Guy.”

If sail deployment goes well, the Planetary Society will be be in a good position for the launch of their next solar-sail vehicle in 2016 aboard SpaceX’s Falcon Heavy rocket.  This vehicle will be put in a higher orbit that the current one, allowing it to use the solar sail for propulsion unencumbered by Earth’s atmospheric drag.