LightSail - Flying to Other Worlds on Sunlight

The Planetary Society’s LightSail 2 spacecraft has reentered Earth’s atmosphere, successfully completing its mission to demonstrate flight by light for small spacecraft. LightSail 2 reentered sometime on Nov. 17, according to orbital predictions.

The reentry completes a mission of nearly three-and-a-half years, during which LightSail 2 showed that it could change its orbit using the gentle push of sunlight, a technique known as solar sailing. LightSail 2 demonstrated that small spacecraft can carry, deploy, and utilize relatively large solar sails for propulsion.

“LightSail 2 is gone after more than three glorious years in the sky, blazing a trail of lift with light, and proving that we could defy gravity by tacking a sail in space,” said Bill Nye, CEO of The Planetary Society. “The mission was funded by tens of thousands of Planetary Society members and backers, who want to advance space technology. And, take a look at these pictures! With this small spacecraft, we provided citizens of Earth with awe-inspiring overviews of our home world.”

LightSail 2 hitched a ride to space in June 2019 aboard a SpaceX Falcon Heavy rocket. It began operations at an altitude of about 720 kilometers (450 miles), where Earth’s atmosphere is still thick enough to create drag and slow down a spacecraft. For reference, the International Space Station orbits at an altitude of roughly 400 kilometers (250 miles).

As atmospheric drag slowly pulled LightSail 2 back towards Earth, the spacecraft successfully used solar sailing to lower its decay rate and on occasion overcome drag completely. After 18,000 orbits and 8 million kilometers (5 million miles) traveled, drag finally won out, bringing the mission to a close.

“During its extended mission LightSail 2 continued to teach us more about solar sailing and achieved its most effective solar sailing, but that was followed by an increase in atmospheric drag in part from increasing solar activity,” said Bruce Betts, LightSail program manager and chief scientist for The Planetary Society. “The spacecraft is gone, but data analyses and sharing of results will continue.”