What looked like a failed mission has turned into an unexpected win for NASA with the successful deployment of the first-ever solar sail in low-Earth orbit. More than a month after the NanoSail-D nanosatellite failed to eject from its parent satellite, engineers at NASA's Marshall Space Flight Center were pleasantly surprised when the 3.9 x 3.9 x 14.9-inch unit spontaneously separated from the Fast Affordable Scientific and Technology Satellite (FASTSAT) last week. On January 20, after a timed three-day countdown, the ultra-thin, 100-square-foot (9.29 m2) polymer sail carried by the nanosatellite was unfurled 404 miles (650 km) above Earth where it will remain in orbit for up to 120 days.

The NanoSail-D was one of six experiments launched aboard FASTSAT in November 2010. The ejection was originally triggered on December 6, but the NanoSail-D became stuck and failed to separate from FASTSAT.

Now, after last week's surprising turn of events, the solar-sail mission will be able to continue with its objectives. As well as demonstrating the deployment of a compact solar sail boom, these objectives include testing the de-orbit potential of the technology. Because the sail experiences drag from the upper atmosphere it will drop from orbit in 70 to 120 days and NASA hopes that this approach can be used to bring down satellites at the end of their lifetime and therefore help clean up space debris.

Solar sail technology also has immense potential as a means of propulsion in space and while the NanoSail-D is likely to experience too much atmospheric drag for the pressure of sunlight on the sail to be measured, NASA still hopes to that the experiment could lead to advances of this use of the technology.

In June last year the Japan Aerospace Exploration Agency's IKAROS space yacht became the first craft to deploy a solar sail in space.

The position of NanoSail-D can be tracked here and the craft will continue to send out beacon signals (at 437.270 MHz) until its onboard batteries are expended. NASA and Spaceweather.com are also running a competition for the best amateur images of NanoSail-D in orbit.

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