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Cal Poly serves as mission control for solar sailing spacecraft

Josh Spradling / The Planetary Society
An artist's concept of LightSail 2 above Earth.

Update July 9, 2019

The deployment of Lightsail 2’s solar sails has been delayed until at least Sunday, July 21. Bruce Betts, Lightsail 2 mission program manager, said the spacecraft is stable and healthy; however, some unexpected behavior in altitude control system sensors has the mission team slowing down. “We don’t want to rush it,” Betts told KCBX News on Tuesday afternoon. “We may have to upload fixes and we want to do it in a methodical way.” KCBX News will continue to check in with the team at Cal Poly for updates.


A unique spacecraft is now orbiting the earth, and soon a team at Cal Poly in San Luis Obispo will command it to unfurl super-thin stretches of Mylar, serving as sails. The craft will then glide along, propelled only by sunlight.

The rocket that transported the spacecraft into orbit launched from Florida’s Kennedy Space Center on June 25, serving similar to a public bus—making several stops and dropping off passengers in Earth’s orbit. One of those passengers is Lightsail 2, a spacecraft decades in the making. And San Luis Obispo’s Cal Poly is a key player in the mission, serving as mission control.

If you’re old enough to have been a Johnny Carson fan, you may recall a 1976 interview on his late-night talk show with the famous astronomer Dr. Carl Sagan. In that interview, Sagan introduced America to a novel idea.

“Carson: Let’s talk about this, this is interesting. Sagan: Well, there’s a tremendously exciting prospect called solar sailing… Carson: solar sailing. Sagan: [It] travels on the radiation and particles that come out of the sun - the wind from the sun.”

43 years later, the concept is now a reality. And it’s crowdfunded.

Here’s astronomer Bill Nye explaining how it works in a Planetary Society video.

“Light is made up of particles we call photons. So imagine this ping pong ball is a photon. A single particle of light. Now, photons weigh nothing, they have no mass, but they still have momentum. If we have a spacecraft that's low enough mass, and big and reflective enough, then photons can give it a little push. Each photon imparts just a tiny bit of momentum, but the Sun pumps out billions and billions of them every second....”

Nye is CEO of the Planetary Society, which was co-founded by Carl Sagan. The Planetary Society an international non-profit that advocates for space exploration, the world’s largest non-governmental space organization. From its members and people around the world giving donations, it crowdsourced the $7 million dollars it cost for the LightSail 2 mission.

“For us, since we’re funded by citizens, we like to say we’re democratizing space,” said Merc Boyan, whose title at the Planetary Society is “Visual Storyteller.” Boyan says the goal of the mission is to prove solar sailing is a viable means to travel through space.

“Because you don't have to bring up fuel,” Boyan told KCBX News in a 2018 interview at Cal Poly, when the Lightsail 2 spacecraft was first packed into its cosmic suitcase, a satellite called a CubeSat. “And that's really one of the hardest things about a spacecraft—you go up into space and you have to bring this fuel to get around. And it either will run out at some point, or be very heavy to get off of the ground.”

Now, the concept Carl Sagan first described in the 1970s is about to solar power a spacecraft into higher and higher orbit. It will orbit the Earth for about a year, soaring higher and higher. Eventually it will fall like Icarus of Greek mythology.

“LightSail 2's attitude control system does not have the precision to maintain a circular orbit and continuously fly the spacecraft higher,” said Jason Davis with the Planetary Society. “Therefore, as one side of LightSail 2’s orbit rises, the other side will dip lower, until atmospheric drag overcomes the forces of solar sailing, ending the primary mission. The spacecraft will remain in orbit roughly a year before entering the atmosphere and burning up.”

As Bill Nye says, if the mission is a success, the descendents of LightSail 2 may someday travel to the stars, fueled by the sun.

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