The LightSail spacecraft, designed and manufactured by The Planetary Society, has lost contact with Earth. The mission, designed to test technologies needed to propel a spacecraft through the action of sunlight, launched on May 20.

The Planetary Society announced it believes the problem is the result of an error in the software controlling the main avionics board.

If the software controlling the main avionics board is found to be the crux of the problem, mission engineers would be forced to reboot the system. Such a procedure would also likely require controllers to initiate a manual opening of the sail aboard the vehicle.

LightSail was operating at normal conditions on May 22, returning data packets to Earth every 15 seconds. Each time information was sent to Earth, a record of the transmission was recorded in an internal file on the spacecraft named beacon.csv. This spreadsheet-like file grows with each new record added to its list. An early version of the software used aboard the vehicle would crash whenever the beacon file grew to 32 megabytes in size, about the same amount of information as six typical songs. Although the developer of the software corrected this glitch, the update was not included on the LightSail.

Ground controllers were warned of the impending crash on May 22, and they devised a software update which would have kept the CubeSat spacecraft running. They planned to send the electronic fix up to the craft during its next pass over the control station. However, communication with the vehicle was lost before mission planners were able to contact the craft.

Before the revolutionary spacecraft fell silent, it returned roughly 140 packets of data back to the ground, to be analyzed by researchers.

"LightSail is likley now frozen, not unlike the way a desktop computer suddenly stops responding. A reboot should clear the contents of the problematic beacon.csv file, giving the team a couple days to implement a fix. But to pull a phrase from recent mission reports, the outcome of the freeze is 'non-deterministic,' " Jason Davis wrote for The Planetary Society.

In other words, just as frozen home computers may or may not re-boot through the use of windows and menus, the spacecraft might not respond to orders to shut down and restart. Personal computers often need to have the power button pressed, crashing the system, to bring the processor back to life. A similar process may now be necessary for this solar-sail spacecraft.

LightSail employs a massive sail, made of Mylar, designed to capture sunlight, propelling it in flights between planetary bodies in the inner solar system.

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