The LightSail 2 spacecraft successfully demonstrated light flight

Years of computer simulations. Countless ground tests. They all lead so far. The Planet Society's spacecraft LightSail 2, which has been built by many people, successfully lifts its orbit solely from the power of sunlight.

Since launching the spacecraft's silver sunbath last week, mission leaders have been optimizing the way the spacecraft navigates during its solar sail. After a few tweaks, LightSail 2 began to orbit around Earth. In the last 4 days the spacecraft has raised its orbital high point, or apogee, by about 2 kilometers. Perigee, or low point in its orbit, has dropped by a similar amount, which is in line with the pre-flight expectation for the effects of atmospheric drag on the spacecraft. The mission team confirmed that the increase in apogee can only be due to sunshine, which means that LightSail 2 has successfully fulfilled its primary goal of demonstrating light flight for CubeSats.

"We are pleased to announce the success of the LightSail 2 mission," said LightSail Program Director and Planetary Society Chief Scientist Bruce Bets. "Our criteria was to demonstrate controlled sunshine on CubeSat by changing the orbit of the spacecraft using only the Sun's light pressure, something that has never been done before. I'm extremely proud of this team. It's been a long time and we've done it . "

The base stone makes LightSail 2 the first spacecraft to use a solar sailboat to propel Earth, the first small spacecraft to demonstrate solar sailing, and simply the second ever spacecraft to successfully fly after Japan's IKAROS launch 2010 LightSail 2 is also the first multi-human-funded spacecraft to successfully demonstrate a new form of propulsion.

"For planetary society, this moment is decades in the making," said Planetary Society Executive Director Bill Nye. "Carl Sagan talked about solar sailing when I was in his class in 1977. But the idea goes back to at least 1607, when Johannes Kepler notes that comet tails must be created by energy from the sun. The mission of LightSail 2 is a game changer for space flight and space exploration advancement. "

On Monday, LightSail 2 sent home a new full-resolution image taken from its camera during the deployment of solar panels. The perspective is the opposite of last week's full-resolution image and shows the canvas more fully unfolded. LightSail 2's alloy Mylar sail shines against the blackness of space, with the Sun peering close to sail on sail.

The mission team will continue to elevate LightSail 2's orbit for about a month as the perigee shrinks to the point where atmospheric traction overcomes the thrust of the sun. During the orbit period, the team will continue to optimize the operation of the solar canvas.

"We have been working on deploying sails to perfect the way the spacecraft tracks the sun," said LightSail 2 project manager Dave Spencer. "The team has done a great job bringing us to the point where we can declare the mission a success. Moving forward, we will continue to work to adjust the effectiveness of sail control and see how much we can increase our peak in time."

One such enhancement involves LightSail 2's single impulse wheel, which rotates the spacecraft sideways and then edges toward the sun each orbit to turn on and off the thrust from the sun's sail. Momentum wheels can "saturate" by hitting predetermined speed limits, after which they are no longer effective at spinning a spacecraft. Most spacecraft use chemical throttles to desaturate inertial wheels; LightSail 2 relies on torque electromagnetic rods to orient the spacecraft by pushing against the Earth's magnetic field.

The LightSail 2 impulse wheel is currently reaching its saturation limit several times a day, and the desaturation of the wheel temporarily takes the spacecraft out of its proper orientation for sunshine. The mission team has already implemented a software update that increases the time between saturation events and is also working to automate the saturation process. Both enhancements should result in improved solar sailing performance.

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