LightSail 2, designed and crowd-funded by the Planetary Society, is a small spacecraft that has been moving around at high-speeds in Earth’s orbit, and turning direction by capturing solar photons with a square sail the size of a boxing ring.
Having launched in July 2019, the vessel has spent over a year meandering about 186 miles (300 kilometers) above the International Space Station, at 460 miles above Earth, it has produced a trove of scientific data which mission engineers at the Planetary Society will use to advance humanity’s understanding of solar sailing—potentially, it will be a very important and reliable form of space travel in the decades to come.
Now LightSail 2 is entering the extended mission phase, where scientists will study how things like orbital decay—the degree to which the spacecraft’s trajectory gradually falls, similar to how a hula hoop falls when it stops spinning—will affect the bread loaf-sized craft as it slowly falls towards Earth and eventually burns up on re-entry.
During our extended mission we’ll continue making changes to our sail control software, which will help future solar sail missions optimize their performanceBruce Betts (Planetary Society chief scientist and LightSail 2 program manager)
The little ship moves at the whim of two powerful forces: gravity and the sun, which one might imagine as acting like an ocean current and the wind.
LightSail 2 is in orbit like a satellite around the earth, and so the scientists must steer, recharge batteries, and take photographs in response to where its orbit, which due to the non-spherical nature of our planet is quite wobbly, takes it.
However, for about 28 minutes of its 100-minute orbit, it can turn its 34-square meter sail, which rather than absorbing the light like normal cloth, repels it thanks to its reflective material called Mylar.
The momentum of mass-less traveling photons bouncing off the sail gives it a slight push to be able to steer itself during those 28 minutes, proving that solar sailing is viable for use in steering and propelling “CubeSats”—smaller satellites that will really push the boundaries of space exploration, not least because a solar-sailing spacecraft doesn’t need chemical propulsion.