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Author Topic:   The Planetary Society's LightSail solar sails
Robert Pearlman
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posted 11-09-2009 05:25 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The Planetary Society release
Planetary Society to Sail Again with LightSail New Project Will Launch Three Separate Solar Sails Over Next Several Years

"We're back!" said Louis Friedman, Executive Director of The Planetary Society. "With an even more ambitious solar sail program than our last venture."

The Planetary Society today announced LightSail, a plan to sail a spacecraft on sunlight alone by the end of 2010. The new solar sail project, boosted by a one-million-dollar anonymous donation, was unveiled at an event on Capitol Hill in Washington, D.C on the 75th anniversary of the birth of Planetary Society co-founder Carl Sagan, a long-time advocate of solar sailing.

LightSail is an innovative program that will launch three separate spacecraft over the course of several years, beginning with LightSail-1, which will demonstrate that sunlight alone can propel a spacecraft in Earth orbit. LightSails 2 and 3, more ambitious still, will reach farther into space.

"We are going to merge the ultra-light technology of nanosats with the ultra-large technology of solar sails in an audacious new program," said Friedman.

Taking advantage of the technological advances in micro- and nano-spacecraft over the past five years, The Planetary Society will build LightSail-1 with three Cubesat spacecraft. One Cubesat will form the central electronics and control module, and two additional Cubesats will house the solar sail module. Cameras, additional sensors, and a control system will be added to the basic Cubesat electronics bus.

"To get sunlight to push us through space, we need a large sail attached to a small spacecraft. Lightsail-1 fits into a volume of just three liters before the sails unfurl to fly on light. It's elegant," exclaimed Planetary Society Vice President Bill Nye the Science Guy.

LightSail seeks to create and prove solar sail technologies that in a few years can

  • monitor the Sun for solar storms,
  • provide stable Earth observation platforms, and
  • explore our solar system without carrying heavy propellants.
Sailing on light pressure (from lasers rather than sunlight) is also the only known technology that might carry out practical interstellar flight, helping pave our way to the stars.

"Sailing on light is a pathway to the stars, but on that path are also some very important scientific and engineering applications that help us understand and protect our own planet and explore other worlds," remarked Planetary Society President Jim Bell.

Reflected light pressure, not the solar wind, propels solar sails. The push of photons against a mirror-bright surface can continuously change orbital energy and spacecraft velocity. LightSail-1 will have four triangular sails, arranged in a diamond shape resembling a giant kite. Constructed of 32 square meters of mylar, LightSail-1 will be placed in an orbit over 800 kilometers above Earth, high enough to escape the drag of Earth's uppermost atmosphere. At that altitude the spacecraft will be subject only to the force of gravity keeping it in orbit and the pressure of sunlight on its sails increasing the orbital energy.

Lightsail-2 will demonstrate a longer duration flight to higher Earth orbits. LightSail-3 will go to the Sun-Earth Libration Point, L1, where solar sails could be permanently placed as solar weather stations, monitoring the geomagnetic storms from the Sun that potentially endanger electrical grids and satellite systems around Earth.

The Planetary Society's attempt in 2005 to launch the world's first solar sail, Cosmos 1, was scuttled when its launch vehicle, a Russian Volna rocket, failed to reach Earth orbit. But the organization's membership never lost faith in the goal to sail on wings of light, and now, thanks to their continued support - including the million dollar private (and anonymous) donation - the new LightSail project will begin.

Sagan's widow and collaborator, Ann Druyan - whose Cosmos Studios was the Society's partner and principal sponsor of Cosmos 1 - serves as Chief Advisor to the current project.

Druyan commented, "Carl and I once wrote 'We have lingered too long on the shores of the cosmic ocean. It's time to set sail for the stars.' We are celebrating his birthday by announcing the maiden voyages of a fleet of ships conceived to fulfill that mythic imperative. I think I know what this would have meant to him."

James Cantrell, CEO of Strategic Space Inc, is Project Manager of LightSail-1. Stellar Exploration will build the spacecraft in San Luis Obispo, CA. Other team participants include the Cubsesat development group at California Polytechnic University, San Luis Obispo, and a team at Russia's Space Research Institute.

Robert Pearlman
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The Planetary Society release
LightSail Has a Launch Date!

The Planetary Society's Highly-Innovative Solar Sail Scheduled to Ride Into Orbit Aboard SpaceX Falcon Heavy, The World's Most Powerful Rocket

The Planetary Society, the world's largest and most influential space interest group, announced Wednesday (July 9) that its LightSail solar sail will reach space on a SpaceX Falcon Heavy launch in 2016.

"It's fantastic that at last we have a launch date for this pioneering mission," said Planetary Society CEO Bill Nye The Science Guy. "When I was in engineering school, I read the book about solar sailing by my predecessor, Society Co-founder Louis Friedman. But the dream of sailing on light alone goes back much further."

The Planetary Society has a long history of solar sail activity. In June 2005, the Society attempted to launch Cosmos 1, which would have been the first solar sail in space. The failure of a Russian booster doomed that effort, but the Society never gave up the dream of sailing the cosmos on the gentle yet constant pressure exerted by sunlight. Solar sailing promises tremendous advantages over traditional chemical rockets. There is no need to carry fuel for complex rocket engines, as the Sun provides an endless source of energy for propulsion. Solar sailing and related techniques have been called the only practical way to reach other stars.

While there have been other solar sail missions in the last decade — notably Japan's IKAROS — none have attempted what LightSail will. First, LightSail is entirely funded by Planetary Society members and other private donors. Further, technologies developed for LightSail may enable other small interplanetary spacecraft to achieve success. The creation and launch of cubesats is now within reach of universities and other organizations that could once only dream of flying their own missions.

Cubesats utilize a standard design based on 10-centimeter (about 4-inch) cubes. LightSail is three cubes, or just 30 centimeters long. Tucked inside this tiny package are four ultra-thin Mylar sails that will be deployed a few weeks after orbital insertion. These brilliantly reflective wings will expand to 32 square meters (344 square feet), making LightSail easily visible to naked eye observers on Earth.

LightSail will reach Medium Earth Orbit (MEO) stored inside another innovative spacecraft: Prox-1 - developed by the Georgia Institute of Technology to demonstrate new technologies enabling two spacecraft to work in close proximity. After ejecting LightSail, the largely student-built Prox-1 will track and image LightSail, including the sail deployment.

Carrying Prox-1 and LightSail to Medium Earth Orbit (MEO) will be the new Falcon Heavy, developed by SpaceX of Hawthorne, California — the most powerful rocket ever built and the largest since the Saturn V that delivered Apollo astronauts to the Moon.

A test flight of LightSail on a smaller rocket may also be conducted in 2015. This flight will only reach low earth orbit (LEO), where there is still too much atmosphere for a solar sail to function. It will nevertheless allow the LightSail team to check the operation of vital systems in the extreme environment of space. That team includes faculty and students at California Polytechnic State University in San Luis Obispo.

Robert Pearlman
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Planetary Society release
Planetary Society Announces Test Flight for Privately Funded LightSail Spacecraft

CEO Bill Nye, Neil deGrasse Tyson, partners invite public to follow May 2015 mission

The Planetary Society today announced the first of its LightSail spacecraft will embark on a May 2015 test flight. Funded entirely by private citizens, the solar sail satellite will hitch a ride to space aboard an Atlas V rocket from Cape Canaveral Air Force Station in Florida. The mission will test LightSail's critical functions, a precursor to a second mission slated for 2016. That second flight will mark the first controlled, Earth-orbit solar sail flight and ride along with the first operational launch of SpaceX's Falcon Heavy rocket.

"There's an old saying in aerospace, 'One test is worth a thousand expert opinions.' After six years of development, we're ready at last to see how LightSail flies," said Bill Nye (The Science Guy), CEO at The Planetary Society.

"LightSail is technically wonderful, but it's also wonderfully romantic. We'll sail on sunbeams," added Nye. "But wait, there's more: this unique, remarkable spacecraft is funded entirely by private citizens, people who think spaceflight is cool."

Solar sailing works by using sunlight for propulsion. When solar photons strike LightSail's reflective Mylar sails, their momentum is transferred to the spacecraft, gradually accelerating it through space. While the push from photons is miniscule, it is continuous and unlimited. Solar sails can eventually reach greater speeds than those obtained from chemical rockets. LightSail consists of four identical triangular sails attached to four 4-meter booms, resulting in a square solar sail when fully deployed.

The 2015 test flight will not carry the spacecraft high enough to escape Earth's atmospheric drag, and will thus not demonstrate controlled solar sailing. Once in orbit, the spacecraft will go through a checkout and testing period of about four weeks before deploying its solar sails. After the sails unfurl, LightSail will test its attitude control system and study the behavior of the sails for a few days before it is pulled back into the planet's atmosphere. Key images and data on the spacecraft's performance will be sent to ground stations at Cal Poly San Luis Obispo and Georgia Tech.

Dr. Neil deGrasse Tyson, Hayden Planetarium director and Planetary Society board of directors member, added, "With the expected launch of LightSail — a craft propelled among the stars on the pressure of light itself — the expanse of space becomes a literal analogue to the open seas. If space is tomorrow's ocean, then Earth's surface is its shoreline."

LightSail is packaged into a small spacecraft called a CubeSat. CubeSats have made low-cost space missions a reality for universities and research groups. However, providing propulsion for these tiny satellites has been a major challenge. LightSail will demonstrate the viability of solar sailing for CubeSats. The spacecraft was designed by Stellar Exploration, Inc., in San Luis Obispo, Calif. LightSail's lead contractor for integration and testing is Pasadena, Calif.-based Ecliptic Enterprises Corporation, a space avionics and sensor systems firm best known for its popular RocketCam™ family of video systems used on rockets and spacecraft.

"Starting with a clever '3U' CubeSat design from Stellar Exploration, a small team at Ecliptic was tasked a year ago with completing the final integration and testing of this first LightSail spacecraft," said Rex Ridenoure, CEO of Ecliptic. "We experienced several design, hardware, software and testing issues along the way, but thanks to excellent technical support from Stellar Exploration, Boreal Space, Half Band Technologies, Cal Poly, Georgia Tech and others, we surmounted them all and succeeded in securing approval to launch."

The Planetary Society's second LightSail spacecraft is scheduled to fly in 2016. This mission will build on the results of the test flight to conduct a full demonstration of solar sailing in Earth orbit. LightSail will be packaged inside a spacecraft called Prox-1 built by students at Georgia Tech. The spacecraft duo will be launched aboard a SpaceX Falcon Heavy rocket to an orbit of about 720 kilometers (450 miles).

The Planetary Society's solar sailing involvement was started by Society co-founder Louis Friedman more than a decade ago. The LightSail project is managed by Doug Stetson, founder and principal partner of the Space Science and Exploration Consulting Group.

"LightSail is truly 'the people's satellite.' Thanks to our members, the dream of citizen supported solar sailing will become a reality; the vision goes back to our founders, Lou Friedman, Bruce Murray, and Carl Sagan. We encourage space fans worldwide to join us on LightSail's journey. Together we can change the world." Nye concluded.

Robert Pearlman
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collectSPACE
Air Force X-37B space plane lifts off on 4th flight, with LightSail in tow

The U.S. Air Force's secret-but-storied X-37B mini-space shuttle is back in orbit, having lifted off on its fourth clandestine mission Wednesday (May 20), with a prototype solar sail in tow.

The unmanned Orbital Test Vehicle (OTV) launched atop a United Launch Alliance (ULA) Atlas V rocket from Cape Canaveral Air Force Station in Florida at 11:05 a.m. EDT (1505 GMT). Hitching a ride with the booster's upper stage were ten small satellites, called CubeSats, to be deployed separately from the space plane – including The Planetary Society's first LightSail.

...the prototype for the non-profit's primary mission, targeted for launch next year, this first LightSail won't attempt solar sailing — it will be too close to the Earth to try. But it will demonstrate deploying the large (344 sq. ft. or 32 sq. m.) Mylar surface that the next LightSail will use to reflect the photons from the sun to accelerate it forward.

"We expect to be in space [on this mission] for about 28 days when deployment will occur, though we may deploy sooner," Bill Nye, the CEO of The Planetary Society, said. "We expect to remain in orbit for anywhere between two and ten days before atmospheric drag pulls the spacecraft down and it burns up on re-entry."

Robert Pearlman
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The Planetary Society release
Bill Nye & Planetary Society Celebrate LightSail Spacecraft Test Launch

Citizen-funded solar sail CubeSat in orbit, awaits sail deployment stage

The Planetary Society's citizen-funded LightSail spacecraft has launched into orbit aboard a United Launch Alliance (ULA) Atlas V rocket from Cape Canaveral Air Force Station. The spacecraft is part of a secondary payload dubbed ULTRASat aboard the U.S. Air Force mission AFSPC-5. The mission will test LightSail's critical functions in low-Earth orbit, a precursor to a second mission set for 2016.

Bill Nye (The Science Guy), CEO at The Planetary Society, witnessed the launch on site among Planetary Society staff and members. Nye stated:

"Today is an extraordinary day for The Planetary Society, our members, and space enthusiasts around the world: LightSail successfully launched into orbit. Our co-founders dreamt of this day. We've been working to get a solar sail into space since I joined The Planetary Society Board in 1997.

"While we celebrate this step, LightSail's biggest tests are still ahead. Over the next days, we will be monitoring our CubeSat as we prepare for the big show: the day LightSail deploys its super shiny Mylar sails for flight on sunlight. Stay tuned; the best is about to happen.

"As we await that stage, we just get more excited. After all, we've been working on this for 39 years. LightSail would not be possible without our members, fans and citizens worldwide. We are all in this together. Let's see if we can give space exploration a strong nudge and change the world a little bit."

Solar sailing works by using sunlight for propulsion. When solar photons strike LightSail's reflective Mylar sails, their momentum is transferred to the spacecraft, gradually accelerating it through space. While the push from photons is miniscule, it is continuous and unlimited. Solar sails can eventually reach greater speeds than those obtained from chemical rockets.

LightSail is packaged into a small spacecraft called a CubeSat. CubeSats have made low-cost space missions a reality for universities and research groups. However, providing propulsion for these tiny satellites has been a challenge. LightSail will demonstrate the viability of solar sailing for CubeSats. During the May 2015 LightSail test launch, the LightSail team will address any technical issues and apply takeaways to the 2016 mission.

The 2015 test flight will not carry the spacecraft high enough to escape Earth's atmospheric drag, and will thus not demonstrate controlled solar sailing. Once in orbit, the spacecraft will go through a checkout and testing period of about four weeks before deploying its solar sails. After the sails unfurl, LightSail will study the behavior of the sails for a few days before it is pulled back into Earth's atmosphere. Key images and data on the spacecraft's performance will be sent to ground stations at Cal Poly San Luis Obispo and Georgia Tech.

The spacecraft was designed by Stellar Exploration, Inc., in San Luis Obispo, Calif. LightSail's lead contractor for integration and testing is Pasadena, Calif.-based Ecliptic Enterprises Corporation, a space avionics and sensor systems firm best known for its popular RocketCam family of video systems used on rockets and spacecraft. The LightSail project is managed by Doug Stetson, founder and principal partner of the Space Science and Exploration Consulting Group.

The Planetary Society's second LightSail spacecraft is scheduled to fly in 2016. This mission will build on the results of the test flight to conduct a full demonstration of solar sailing in Earth orbit. LightSail will be packaged inside a spacecraft called Prox-1 built by students at Georgia Tech. The spacecraft duo will be launched aboard a SpaceX Falcon Heavy rocket to an orbit of about 720 kilometers (450 miles).

Citizens around the world can be part of the 2016 LightSail mission. The "Selfies to Space" feature invites people to submit photographs for inclusion aboard the spacecraft at planetary.org/selfie.

Dr. Neil deGrasse Tyson, a member of The Planetary Society board of directors, joined Nye to launch a LightSail Kickstarter campaign in a video announcement, which led to immediate worldwide response. Funded entirely by private citizens, LightSail is the yield of collective support.

The Planetary Society's solar sailing involvement was started by Society co-founder Louis Friedman more than a decade ago. Co-founder Carl Sagan championed solar sailing on a famous 1976 episode of The Tonight Show with Johnny Carson. For complete coverage of the LightSail test flight, as well as the second LightSail mission scheduled for 2016, visit sail.planetary.org.

Robert Pearlman
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The Planetary Society update
Software Glitch Pauses LightSail Test Mission

The Planetary Society's LightSail test mission is paused while engineers wait out a suspected software glitch that has silenced the solar sailing spacecraft. Following a successful start to the mission last Wednesday (May 20), LightSail spent more than two days sending about 140 data packets back to Earth.

But the long Memorial Day weekend here in the United States offered no respite for the LightSail team, as they scrambled to figure out why the spacecraft's automated telemetry chirps suddenly fell silent. It is now believed that a vulnerability in the software controlling the main avionics board halted spacecraft operations, leaving a reboot as the only remedy to continue the mission. When that occurs, the team will likely initiate a manual sail deployment as soon as possible.

What happened?

As of late Friday afternoon (May 22), LightSail was continuing to operate normally. The spacecraft's ground stations at Cal Poly San Luis Obispo and Georgia Tech were receiving data on each pass. Power and temperature readings were trending stably, and the spacecraft was in good health.

But inside the spacecraft's Linux-based flight software, a problem was brewing. Every 15 seconds, LightSail transmits a telemetry beacon packet. The software controlling the main system board writes corresponding information to a file called beacon.csv. If you're not familiar with CSV files, you can think of them as simplified spreadsheets — in fact, most can be opened with Microsoft Excel.

As more beacons are transmitted, the file grows in size. When it reaches 32 megabytes — roughly the size of ten compressed music files — it can crash the flight system. The manufacturer of the avionics board corrected this glitch in later software revisions. But alas, LightSail's software version doesn't include the update.

Late Friday, the team received a heads-up warning them of the vulnerability. A fix was quickly devised to prevent the spacecraft from crashing, and it was scheduled to be uploaded during the next ground station pass. But before that happened, LightSail fell silent. The last data packet received from the spacecraft was May 22 at 21:31 UTC (5:31 p.m. EDT).

The aftermath

LightSail is likley now frozen, not unlike the way a desktop computer suddenly stops responding. A reboot should clear the contents of the problematic beacon.csv file, giving the team a couple days to implement a fix. But to pull a phrase from recent mission reports, the outcome of the freeze is "non-deterministic." That means sometimes the processor will still accept a reboot command; other times, it won't. It's similar to the way you deal with a frozen computer: You can try to struggle past sluggish menus and click reboot, but sometimes, your only recourse is pressing the power button.

As of Tuesday afternoon (May 26), there have been 37 Cal Poly and Georgia Tech ground station passes. During half of those, reboot commands were sent to the spacecraft. Nothing has happened yet. Therefore, we have to assume that LightSail is only going to respond to the power button method.

When I [Jason Davis] filmed an interview with our CEO, Bill Nye, and system engineer Barbara Plante, last year, Nye points out a piece of hardware strapped to BenchSat, LightSail's acrylic-mounted testing clone:

"There's nobody in outer space to push that reset button," says Nye.

"No one that we've gotten to volunteer for that job," Plante replies. "But it's open."

Since we can't send anyone into space to reboot LightSail, we may have to wait for the spacecraft to reboot on its own. Spacecraft are susceptible to charged particles zipping through deep space, many of which get trapped inside Earth's magnetic field. If one of these particles strikes an electronics component in just the right way, it can cause a reboot. This is not an uncommon occurrence for CubeSats, or even larger spacecraft, for that matter. Cal Poly's experience with CubeSats suggest most experience a reboot in the first three weeks; I spoke with another CubeSat team that rebooted after six. Coincidentally, this is close to the original 28-day sail deployment timeline.

Next steps

Cal Poly and Georgia Tech will keep listening for LightSail on each ground pass. Furthermore, Cal Poly is automating the reboot command transmission to be sent few ground station passes, on the hope that one command sneaks through (we don't send the command on every pass because a successful reboot triggers a waiting period before beacon transmissions begin). But as of right now, we can't do much except wait, hoping a charged particle smacks the spacecraft in just the right way to cause a reboot. LightSail is capable of remaining in orbit about six months in its CubeSat form.

In the meantime, the team is looking at several fixes to work around the software vulnerability once contact is reestablished. One is a Linux file redirect that would send the contents of the troublesome beacon.csv file to a null location, a sort-of software black hole. Lab testing on this fix has been promising — over a gigabyte of beacon packets have already been sent into nothingness without a system freeze.

When we hear from LightSail again, the team will likely initiate a manual sail deployment as soon as possible. Planning has already started on that front — we'll keep you updated.

In the meantime, I'll be refreshing the spacecraft's raw telemetry packet repository, ready to jump at the first sign of new data. With a little luck, the test mission isn't over just yet. Hopefully LightSail will follow trends established by other CubeSat missions and reboot soon.

Robert Pearlman
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The Planetary Society release
Solar Sail Spacecraft Contact Restored After Software Glitch Paused Communications

After a successful launch into orbit aboard a United Launch Alliance Atlas V rocket out of Cape Canaveral, The Planetary Society's LightSail spacecraft went silent after two days of communications. The solar sailing spacecraft test mission, a precursor to a 2016 mission, has now resumed contact after a suspected software glitch affected communications. The LightSail team will soon determine when to attempt deployment of the spacecraft's Mylar solar sails.

Bill Nye (The Science Guy), CEO at The Planetary Society, issued the following statement:

"Our LightSail called home! It's alive! Our LightSail spacecraft has rebooted itself, just as our engineers predicted. Everyone is delighted. We were ready for three more weeks of anxiety. In this meantime, the team has coded a software patch ready to upload. After we are confident in the data packets regarding our orbit, we will make decisions about uploading the patch and deploying our sails — and we'll make that decision very soon. This has been a roller coaster for us down here on Earth, all the while our capable little spacecraft has been on orbit going about its business. In the coming two days, we will have more news, and I am hopeful now that it will be very good."

Robert Pearlman
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The Planetary Society release
LightSail Falls Silent; Battery Glitch Suspected

The LightSail test spacecraft has fallen silent for a second time, less than a day after completing what appeared to be a successful solar panel deployment. Mission managers believe the CubeSat's batteries are in a safe mode-like condition designed to protect the electronics until power levels are safe for operations.

In an e-mail summary sent this afternoon, mission manager David Spencer said before contact was lost, LightSail's batteries did not appear to be drawing current from the solar arrays; nor were they properly shunting power to the spacecraft's subsystems.

"Following solar panel deployment," he wrote, "it was noticed that all of the battery cells were drawing near zero current. This indicated that the batteries were likely in a fault condition stemming from the solar panel deployment event."

On the next ground station overflight, the team regained contact. But the battery situation remained unchanged, and the spacecraft appeared to have rebooted unexpectedly. "The flight team discussed the option of commanding an emergency solar sail deployment, Spencer said. "However, all ground testing of solar sail deployment had been performed under battery power, with all battery cells online and fully charged. It was considered to be doubtful that the sail deployment could be successfully completed without battery power (relying only upon direct input from the solar cells). The flight team decided to address the electrical power subsystem issue and approach solar sail deployment in a known state consistent with ground testing."

LightSail's last automated telemetry chirps came in Wednesday at 4:40 p.m. EDT (20:40 UTC). The spacecraft then moved out of range for ten-and-a-half hours. When Thursday's expected contact time arrived, LightSail was silent.

There were 11 ground station overflights today, but LightSail has yet to phone home. Commands were sent "in the blind" to activate the radio system, but there was no status change. The team opted not to command the spacecraft further until the situation is better understood. LightSail's power system can enter a variety of failsafe conditions based on the behavior of the batteries. Engineers at Ecliptic Enterprises Corporation are working through a complex fault tree to determine the spacecraft's likely state, as well as options for moving forward.

If LightSail is suffering from a chronic undervoltage condition, help could arrive naturally, Spencer said. "The spacecraft orbit is in a geometry where eclipse occurs roughly 2100 seconds each orbit. This is near the maximum eclipse duration that LightSail-A will experience during the mission. Over the next couple of weeks, the orbit will precess to a full-sun condition, where the entire orbit is sunlit."

When contact with LightSail is reestablished, the sail deployment sequence will likely be triggered as soon as battery levels are healthy enough to proceed.

Robert Pearlman
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The Planetary Society release
LightSail Drama Continues as Spacecraft Wakes for Second Time

LightSail is back in business, following the second extended outage of the test spacecraft's mission. The CubeSat checked in at 2:21 p.m. EDT (18:21 UTC) Saturday for the first time since Wednesday afternoon. Over the course of two overflights, 23 beacon telemetry packets were received by the spacecraft's Cal Poly San Luis Obispo ground station.

A rapid sail deployment was briefly considered, but with battery levels still unsteady and just one ground pass remaining before an eight-and-a-half hour outage, the team scrapped the idea. When LightSail came around the Earth again, telemetry showed its batteries were charging—the first time since solar panel deployment three days ago.

If battery levels continue to trend stably during Sunday's early morning ground station passes, sail deployment will be scheduled for 2:02 p.m. EDT (18:02 UTC).

Engineers have been working to narrow down the reason LightSail's batteries tripped into a safe mode-like condition following solar panel deployment. Before this afternoon's signal acquisition, the leading theory was that the spacecraft was stuck in a loop where power levels were too low in Earth's shadow, but too high in sunlight. This power ping-pong could have prevented the batteries from reattaching their circuits to the spacecraft and allowing normal operations to resume. The analysis is still ongoing.

Robert Pearlman
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The Planetary Society release
Deployment! LightSail Boom Motor Whirrs to Life

LightSail's tiny solar sail deployment motor sprung to life Sunday afternoon (June 7), marking an important milestone for The Planetary Society's nail-biting test mission. Sail deployment began at 3:47 p.m. EDT (19:47 UTC) off the coast of Baja California, Mexico, as the spacecraft traveled northwest to southeast.

Telemetry received on the ground showed motor counts climbing to the halfway point before LightSail traveled out of range. Power levels were consistent with ground-based deployment tests, and the spacecraft's cameras were on. "All indications are that the solar sail deployment was proceeding nominally," wrote mission manager David Spencer in an email update.

LightSail is currently out of range until 2:26 a.m. EDT Monday. Ground control teams at Cal Poly San Luis Obispo and Georgia Tech will begin transferring the spacecraft's images from its cameras to flight system. A full-resolution image will be downloaded shortly thereafter.

In the meantime, radio operators around the world are encouraged to listen for LightSail and submit data (details can be found at the bottom of our Mission Control page), which could be invaluable in helping determine the spacecraft's status before tomorrow morning's overflights. Two ground-based observatories will also be attempting to image the spacecraft, and amateur astronomers are encouraged to participate. The spacecraft's current estimated position, along with details for radio trackers, can be found on our mission control page. All photographs and radio data can be submitted here.

LightSail Viewing Tips

Interested in catching a glimpse of LightSail as it soars across the sky? Here are a few viewing tips:

Our Mission Control Center predicts the next time LightSail will fly over your current location. Predictions are based on your device's current location. If you'd like to specify a different spot, head over to N2YO.com and click "Set your custom location." You'll need to create a free account.

The start and end horizons are the locations LightSail should appear and disappear. Max elevation indicates how high it will get in the sky. Zero degrees is the horizon (assuming no obstructions), and 90 degrees is directly overhead.

Look for flyovers that occur around dawn and dusk. The best time to see any spacecraft — including LightSail — is when you are standing in Earth's shadow but the spacecraft is still illuminated by sunlight.

LightSail may be running ahead of schedule. Depending on how long it's been since we've received an orbital update from the Joint Space Operations Center, our pass predictions may be inaccurate. If you're going outside to look, consider starting a few minutes earlier than our listed times.

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The Planetary Society release
Bill Nye & Planetary Society Celebrate LightSail Test Mission Landmark

Data indicate citizen-funded spacecraft deploys solar sail, milestone for test path toward 2016 mission

After 19 days on orbit, data indicate that The Planetary Society's LightSail spacecraft deployed its Mylar solar sail in space. More information will be downloaded, analyzed and publicized in days to come, including possible images.

Today's deployment marked a milestone for the mission to test LightSail's critical functions in low-Earth orbit, a precursor to a second mission set for 2016. Bill Nye (The Science Guy), CEO at The Planetary Society, celebrated the landmark and stated:

"We couldn't get signals to and from our LightSail on the first orbital pass, so we tried again on our next orbit — and it worked! We've learned a lot about perseverance on this test mission. Although it's in inertial space, LightSail has had me on a rollercoaster. I want to thank the engineering team; they've done fantastic work. I especially want to thank our supporters and members, who made this success possible. We are advancing space science and exploration. This mission is part of our mission."

The Planetary Society's solar sailing involvement was started by Society co-founder Louis Friedman more than a decade ago. The spacecraft was designed by Stellar Exploration, Inc., in San Luis Obispo, Calif. LightSail's lead contractor for integration and testing is Pasadena, Calif.-based Ecliptic Enterprises Corporation, a space avionics and sensor systems firm best known for its popular RocketCam family of video systems used on rockets and spacecraft. The spacecraft has ground stations at California Polytechnic State University San Luis Obispo and Georgia Tech. The LightSail project is managed by Doug Stetson, founder and principal partner of the Space Science and Exploration Consulting Group. Boreal Space and Half-Band Technologies are contractors to Ecliptic.

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LightSail Test Mission Declared Success; First Image Complete

The Planetary Society's LightSail test mission successfully completed its primary objective of deploying a solar sail in low-Earth orbit, mission managers said Tuesday (June 9).

During a ground station pass over Cal Poly San Luis Obispo that began at 1:26 p.m. EDT (17:26 UTC), the final pieces of an image showcasing LightSail's deployed solar sails were received on Earth. The image confirms the sails have unfurled, which was the final milestone of a shakedown mission designed to pave the way for a full-fledged solar sail flight in 2016.

The mission began May 20 with a launch from Cape Canaveral aboard a United Launch Alliance Atlas V rocket. The spacecraft fought its way through software glitches, two signal losses and unexpected battery behavior before finally deploying its solar sails on June 7.

The LightSail team is now downloading a second camera image from the opposite side of the spacecraft before it reenters Earth's atmosphere. Because LightSail was directly between the sun and Earth at the time of image acquisition on June 8, it is believed the second photograph may include a view of Earth.

Next, engineers may "walk out" the sail booms to increase the tension on the sails, which could further flatten the wavy appearance of the Mylar. The image also appears slightly distorted due to the camera's fish-eye lens. The team will analyze all sail imagery and any tensioning results in preparation for next year's flight, when LightSail operates in a higher orbit and uses sunlight for propulsion.

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LightSail 2 set to launch aboard SpaceX Falcon Heavy rocket

The Planetary Society's LightSail 2 spacecraft is ready to embark on a challenging mission to demonstrate the power of sunlight for propulsion.

Weighing just 5 kilograms, the loaf-of-bread-sized spacecraft, known as a CubeSat, is scheduled to lift off on June 24, 2019, aboard a SpaceX Falcon Heavy rocket from Kennedy Space Center, Florida. Once in space, LightSail 2 will deploy a boxing ring-sized solar sail and attempt to raise its orbit using the gentle push from solar photons.

It's the culmination of a 10-year project with an origin story linked to the three scientist-engineers who founded The Planetary Society in 1980.

"Forty years ago, my professor Carl Sagan shared his dream of using solar sail spacecraft to explore the cosmos. The Planetary Society is realizing the dream," said Planetary Society CEO Bill Nye. "Thousands of people from all over the world came together and supported this mission. We couldn't have done it without them. Carl Sagan, and his colleagues Bruce Murray and Louis Friedman, created our organization to empower people everywhere to advance space science and exploration. We are go for launch!"

If successful, LightSail 2 will become the first spacecraft to raise its orbit around the Earth using sunlight. While light has no mass, it has momentum that can be transferred to other objects. A solar sail harnesses this momentum for propulsion. LightSail 2 will demonstrate the application of solar sailing for CubeSats, small, standardized spacecraft that have made spaceflight more affordable for academics, government organizations, and private institutions.

LightSail 2 will ride to space aboard the Department of Defense's Space Test Program-2 (STP-2) mission scheduled for launch on June 24, 2019, which will send 24 spacecraft to three different orbits. LightSail 2 itself will be enclosed within Prox-1, a Georgia Tech-designed spacecraft originally built to demonstrate close-encounter operations with other spacecraft. Prox-1 will deploy LightSail 2 seven days after launch.

After a few days of health and status checks, LightSail 2's four dual-sided solar panels will swing open. Roughly a day later, four metallic booms will unfurl four triangular Mylar sails from storage. The sails, which have a combined area of 32 square meters, will turn towards the Sun for half of each orbit, giving the spacecraft a tiny push no stronger than the weight of a paperclip. For about a month after sail deployment, this continual thrust should raise LightSail 2's orbit by a measurable amount.

The Planetary Society launched a nearly identical spacecraft called LightSail 1 in 2015 that successfully tested the spacecraft's sail deployment system. LightSail 2 will fly to an orbit 720 kilometers high, where the acceleration from sunlight overcomes atmospheric drag. The spacecraft may be visible in the night sky for a year to observers within 42 degrees of the equator, which includes the U.S. as far north as Chicago and New York.

The Society launched a larger sail named Cosmos 1 in 2005 that did not reach orbit after a failure of the spacecraft's Russian-built rocket. Planetary Society co-founder Louis Friedman led a 1970s NASA solar sail study that would have sent a spacecraft to rendezvous with Halley's Comet. Fellow Society co-founder Carl Sagan showed off a model of the spacecraft on The Tonight Show with Johnny Carson in 1976.

Results from the LightSail 2 mission are already helping to inform future solar sail projects by other organizations. NASA's NEA Scout spacecraft will launch to the Moon aboard the first Space Launch System flight and use a solar sail to visit a near-Earth asteroid. The Planetary Society shares LightSail project data with NASA through a Space Act Agreement.

The LightSail project started in 2009. The spacecraft was built by Stellar Exploration, Inc. The lead contractor for integration and testing is Ecliptic Enterprises Corporation, with testing, storage and ground support provided by Cal Poly San Luis Obispo. Planetary Society Chief Scientist Bruce Betts serves as the LightSail program manager. The project manager and mission manager is Purdue University's David Spencer.

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The Planetary Society Celebrates Launch of LightSail 2

LightSail 2 is officially in space! The Planetary Society's solar sail CubeSat lifted off from Kennedy Space Center, Florida on 25 June at 02:30 EDT (06:30 UTC). The late-night launch came courtesy of SpaceX's triple-booster Falcon Heavy rocket, which was carrying 24 spacecraft for the U.S. Air Force's STP-2 mission.

Launch was originally scheduled to occur at 23:30 EDT on 24 June (03:30 UTC on 25 June). SpaceX delayed the liftoff time by 3 hours to complete additional ground system checkouts.

During its ride to orbit, LightSail 2 was tucked safely inside its Prox-1 carrier spacecraft. The Falcon Heavy upper stage's payload stack released Prox-1 about an hour and 20 minutes after liftoff, at an altitude of roughly 720 kilometers. Prox-1 will house LightSail 2 for 1 week, allowing time for other vehicles released into the same orbit to drift apart so each can be identified individually. LightSail 2 deployment is set for 2 July.

"After that spectacular nighttime launch, the flight team is ready to operate the LightSail 2 spacecraft," said LightSail 2 project manager David Spencer. "We will be listening for the radio signal in a week, following the release of LightSail 2 from Prox-1."

Bruce Betts, Planetary Society chief scientist and LightSail 2 program manager, added, "After years of hard work we are ecstatic with the launch and looking forward to doing some solar sailing."

In a video message to Planetary Society members, CEO Bill Nye, said, "The SpaceX Falcon Heavy took our spacecraft up and on orbit, thanks to you. Thank you all so much. We are advancing space science and exploration. We are democratizing space. We are innovating."

About 500 Planetary Society members and supporters were on hand at the Kennedy Space Center Apollo-Saturn V Center to watch their crowdfunded spacecraft take flight. Sound from the Falcon Heavy's 27 engines rumbled through the viewing area, as the rocket blazed high into the sky before starting its arc out over the Atlantic Ocean. Both of the rocket's side boosters flew back to Cape Canaveral for upright landings, creating sonic booms that delighted the raucous crowd.

SpaceX's live feed from mission control in Hawthorne, California followed the rocket's center booster as it attempted to land on the drone ship Of Course I Still Love You. The booster's exhaust plume briefly appeared on camera before apparently crashing into the ocean. The landing was not a requirement for mission success.

Meanwhile, the upper stage blasted on to its first stop, an orbit roughly 865 by 300 kilometers above Earth. There, it deployed several CubeSats and a small satellite before lighting its engine again and flying to a circular orbit of about 720 kilometers. Prox-1 was the first spacecraft off the rocket there.

LightSail 2 team members will soon converge at Cal Poly San Luis Obispo in California, where the spacecraft's mission control is located. Once LightSail 2 is released from Prox-1 on 2 July, the team will spend several days checking out the CubeSat's systems before commanding its dual-sided solar panels to deploy. Following that, the spacecraft's solar sails will be deployed, roughly 2 weeks in total from launch day.

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First Contact! LightSail 2 Phones Home to Mission Control

The Planetary Society's LightSail 2 spacecraft sprang loose from its Prox-1 carrier vehicle as planned today (July 2), and sent its first signals back to mission control at Cal Poly San Luis Obispo in California.

The CubeSat, about the size of a loaf of bread, was scheduled to leave Prox-1 precisely 7 days after both spacecraft successfully flew to orbit aboard a SpaceX Falcon Heavy rocket. Following deployment from its spring-loaded enclosure known as a P-POD, LightSail 2 deployed its radio antenna and began transmitting health and status data, as well as a morse code beacon indicating its call sign. The mission team received LightSail 2's first signals on 2 July at 01:34 PDT (08:34 UTC), as the spacecraft passed over Cal Poly.

"The Georgia Tech Prox-1 spacecraft did its job perfectly, delivering LightSail 2 to the desired orbit for solar sailing," said LightSail 2 project manager Dave Spencer. "Receiving the initial radio signal from LightSail 2 is an important milestone, and the flight team is excited to begin mission operations."

"We're all very happy — after years of preparation, we are flying an operational spacecraft!" added Bruce Betts, LightSail program manager and Planetary Society chief scientist.

More data collected during additional ground station passes today will be used to evaluate the health and status of the spacecraft. The next available opportunity for contact is 3 July at roughly 00:30 UTC (2 July at 20:30 EDT), when LightSail 2 flies over Georgia Tech.

The team will spend about a week checking out LightSail 2's systems, exercising the spacecraft's momentum wheel, and taking camera test images before and after deployment of the CubeSat's dual-sided solar panels. Following the successful completion of these tests, the team will deploy the 32-square-meter solar sail, about the size of a boxing ring. A time for the solar sail deployment attempt will be announced later.

The Planetary Society will soon release a dashboard that displays LightSail 2 health telemetry, shows the spacecraft's current position, and offers predictions for when it will pass over your location. LightSail 2 will not be visible to the naked eye until after sail deployment.

Once LightSail 2 deploys its solar sail, it will begin turning the sail into and away from the Sun's rays each orbit, giving the spacecraft a gentle push. The goal is to raise the spacecraft's orbit by a measurable amount over the course of a month. After that, the perigee, or low point, of LightSail 2's orbit is expected to drop too far into Earth's atmosphere for the thrust from solar sailing to overcome atmospheric drag. The spacecraft will remain in orbit about a year before entering the atmosphere and burning up.

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Here are the First Pictures of Earth from LightSail 2

The first pictures from The Planetary Society's LightSail 2 mission are on the ground!

Flight controllers successfully deployed the CubeSat's dual-sided solar panels Friday evening, as it flew south of mission control at Cal Poly San Luis Obispo in California. Pictures taken moments later from the spacecraft's solar panel-mounted cameras show a crescent Earth, as LightSail 2 heads into orbital sunset.

Above: LightSail 2 captured this picture of Earth's limb on 6 July 2019 at 04:41 UTC from a camera mounted on its dual-sided solar panels. The spacecraft was headed into orbital sunset at the time, and the Sun is visible to the right. The picture is unmodified and shows a number of lens flare artifacts caused by sunlight scattering around the camera optics. The spacecraft's dual fisheye cameras have fields of view of about 180 degrees, causing the arcs in the corners and some distortion.

The spacecraft remains healthy since deploying from its Prox-1 carrier vehicle 5 days ago on 2 July. Team members are continuing to prepare the spacecraft for sail deployment, which is expected to occur no earlier than Monday, 8 July during a series of ground station passes between 15:00 and 22:30 PDT (22:00 July 8 to 05:30 July 9 UTC). A decision on whether to proceed with sail deployment Monday will not be made until after spacecraft operations Sunday night.

In addition to deploying LightSail 2's solar panels and downloading imagery, the team successfully activated the spacecraft's momentum wheel, completing crucial tests to ensure it was ready to swing the spacecraft into and out of the Sun's rays each orbit when solar sailing.

Above: LightSail 2 captured this picture of Earth's limb on 6 July 2019 at 04:42 UTC from a camera mounted on its dual-sided solar panels. The spacecraft was headed into orbital sunset at the time, and the Sun is just out of frame on the right side. The picture is unmodified and shows a number of lens flare artifacts caused by sunlight scattering around the camera optics. The spacecraft's dual fisheye cameras have fields of view of about 180 degrees, causing the arcs in the corners and some distortion. The objects in the foreground are believed to be pieces of spectraline, a fishing line-like material used to hold the panels closed prior to deployment.

The team also captured imagery from LightSail 2's cameras prior to solar panel deployment that show the inside of the spacecraft, but opted not to downlink high-resolution versions. The U.S. Air Force has not yet issued position data for LightSail 2, meaning ground-based antennas must currently be aimed at Prox-1 and then adjusted based on Doppler shifts in LightSail 2's signal. This lack of precision position information increases the time required for large file transfers with the spacecraft. We expect the Air Force to issue LightSail 2 position data as soon as Monday.

Above: These low-resolution images show the inside of LightSail 2 prior to solar panel deployment, as seen by the spacecraft's 2 solar panel-mounted cameras. The images have been enlarged 3 times their original sizes. The top 2 and bottom 2 images are the same view from the same camera, under slightly different lighting conditions.

Most of the tasks required to proceed with solar sail deployment are complete. The most significant step left is testing the spacecraft's attitude control system. When solar sailing, LightSail 2's attitude control system orients the spacecraft based on readings from magnetometers and Sun sensors, combined with ground-uploaded position data.

During orbital testing, LightSail 2's magnetometers provided readings that were inconsistent with each other. The team is reviewing ground test data to better understand the situation and develop corrective actions. They are also working to refine the operation of the spacecraft's electromagnetic torque rods, which are used to change the spacecraft orientation. The torque rods are commanded by LightSail 2's attitude control system algorithm, and mission operators have detected sluggish performance. A solution has been developed that will be tested later today.

Upcoming events:

  • Solar sail deployment: No earlier than Monday, 8 July during a series of ground station passes between 15:00 and 22:30 PDT (22:00 July 8 to 05:30 July 9 UTC).

  • Orbit raising: Roughly 30 days following solar sail deployment.

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LightSail 2 Team to Conduct More Testing Before Sail Deployment

The LightSail 2 mission team has delayed deployment of the spacecraft's solar sail until at least 21 July 2019, to conduct additional attitude control system testing and potentially update the spacecraft's flight software. LightSail 2 remains stable and healthy in orbit, and returned another picture to mission control at Cal Poly San Luis Obispo in California.

Communications with the spacecraft have improved thanks to new tracking information provided by the U.S. Air Force. During ground passes Monday, the mission team worked to refine the operation of the spacecraft's electromagnetic torque rods, which turn the spacecraft around each of its three axes, and investigated a difference in readings from two magnetometers.

During additional tests, flight controllers saw unexpected results from the spacecraft's attitude control system, which is essential for orienting LightSail 2 during solar sailing. The team will spend the next several days comparing in-flight sensor readings with ground test data, reviewing the spacecraft's attitude control system algorithm, and potentially updating the flight software.

"We want to take some of the time pressure off the team and make sure that they can methodically address the problems that have been uncovered," said LightSail 2 mission manager Dave Spencer. "Accurate attitude control is critical for the success of the mission, and we are going to take the time to get it right and verify proper functionality before deploying the sail."

With its solar sail stowed, LightSail 2 will remain stable in its current orbit. Once the sail is out, increased atmospheric drag will limit to about 1 month the time the spacecraft can raise its orbit. Therefore it is critical that the attitude control system is working as expected prior to sail deployment.

"The spacecraft is healthy and we have every expectation that we'll be able to resolve this issue," said LightSail program manager and Planetary Society chief scientist Bruce Betts. "Our members and backers have waited a long time to see this project come to fruition, and we want to make sure we maximize our chances for success."

The spacecraft continues to communicate with all four of its ground stations at Cal Poly San Luis Obispo, Georgia Tech, Purdue University, and Kauai Community College.

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LightSail 2 Sail Deployment Scheduled

The Planetary Society's LightSail 2 spacecraft is almost ready to go solar sailing.

Mission officials today cleared the spacecraft for a possible sail deployment attempt on Tuesday, 23 July 2019, during a ground station pass that starts at roughly 11:22 PDT (18:22 UTC). A backup pass is available the following orbit starting at 13:07 PDT (20:07 UTC). These times may change slightly as new orbit predictions become available.

On 17 July, flight controllers placed LightSail 2's attitude control system into solar sailing mode for a second time, allowing it to track the Sun and make two 90-degree turns into and away from the solar photons. When the solar sail has been deployed, these turns will raise one side of the spacecraft's orbit.

An initial review of data from the test showed LightSail 2 performed as expected. A more thorough review is scheduled for Saturday, and on Sunday, the spacecraft will be placed in solar sailing mode a third time as a final verification that it is ready for sail deployment.

Prior to the deployment attempt, LightSail 2 will fly within range of its ground station at Kauai Community College, which will give flight controllers a chance to assess the spacecraft's status one final time.

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The Planetary Society's LightSail 2, now fully deployed, is the first spacecraft in Earth orbit to be propelled only by sunlight.
At 2:47 Eastern time on July 23, the big moment came—four cobalt-alloy booms extended like a tape measure, pulling with them four triangular Mylar sails.

The whole deployment took about three minutes. Soon, LightSail 2 will begin to live up to its name.

"We use the term boom just like on a sailboat, to hold the sails out, because we're twisting relatively fast in Earth orbit," explained Bill Nye, former host of Bill Nye the Science Guy and now CEO of the nonprofit Planetary Society, to the press before launch. "We go edge on toward the sun, twist 90 degrees, go face on and get a full push like a sailboat going downwind, building orbital energy. [We] then twist again on the night side of the Earth and twist on the day side, over and over."

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LightSail 2 Successfully Deploys Solar Sail

The Planetary Society's LightSail 2 spacecraft has successfully deployed the large, aluminized Mylar sail it will use to raise its orbit solely with sunlight.

Flight controllers at Cal Poly San Luis Obispo in California commanded the spacecraft to deploy its solar sails yesterday at about 11:47 PDT (18:47 UTC). Images captured during the deployment sequence and downloaded today show the 32-square-meter sail, which is about the size of a boxing ring, deploying as the spacecraft flew south of the continental United States.

Milestone Achieved

Sail deployment marks a major milestone for the LightSail 2 mission, which aims to demonstrate solar sailing as a viable method of propulsion for CubeSats—small, standardized satellites that have lowered the cost of space exploration.

"Yesterday, we successfully set sail on beams of sunlight," said Bill Nye, CEO of The Planetary Society. "Thanks to our team and our tens of thousands of supporters around the world, the dream started by The Planetary Society's founders more than 4 decades ago has taken flight."

Above: View of the deployment of half of LightSail 2's square sail from Camera 1, which happened on 23 July 2019 at 18:47 UTC. The animation runs at about 100 times actual speed.

Bruce Betts, Planetary Society chief scientist and LightSail program manager, added, "We're ecstatic! The mission team has worked for years to get to this moment when we can start solar sailing."

Following the start of sail deployment on 23 July, telemetry from LightSail 2 showed the spacecraft's small motor was rotating properly, extending four, 4-meter cobalt-alloy booms from their central spindle. The booms unwind like carpenter's tape measures and are attached to 4 triangular sail sections that together form the square solar sail.

Though the motor activity itself was a good indicator of success, confirmation that the sails deployed successfully was only possible via imagery from LightSail 2's dual cameras. The cameras have 185-degree fields of view, and together can image the entire sail from the main LightSail bus, which is about the size of a loaf of bread.

"The successful deployment of the solar sail and the onset of sail control completes our critical post-launch phase," said LightSail 2 project manager David Spencer. "Now we are prepared for the solar sail's mission, to track how the orbit changes and evaluate solar sailing performance."

Above: View of the deployment of half of LightSail 2's square sail from Camera 2, which happened on 23 July 2019 at 18:47 UTC. The animation runs at about 100 times actual speed.

The deployment milestone comes 4 weeks after LightSail 2 launched from Kennedy Space Center, Florida aboard a SpaceX Falcon Heavy rocket, and 3 weeks after the Georgia Tech student-built Prox-1 spacecraft deployed LightSail 2 into orbit. The mission team spent a week checking out the spacecraft's systems before rescheduling sail deployment to allow extra time for testing and tuning the attitude control system.

Preliminary data shows LightSail 2 is already turning its solar sail broadside to the Sun once per orbit, giving the spacecraft a gentle push no stronger than the weight of a paperclip. Solar photons have no mass, but they have momentum, and as they reflect off the solar sail, some of that momentum is transferred and creates thrust. While this thrust is slight, it is continuous and over time will raise LightSail 2's orbit.

LightSail 2 Orbit Raising

The orbit-raising portion of the mission will last about 1 month. LightSail 2 does not have the capability to circularize its orbit—as one side of the spacecraft's orbit raises due to solar sailing, the other side will dip lower into Earth's atmosphere, until atmospheric drag overcomes the slight force from solar sailing. LightSail 2 is expected to reenter the atmosphere in roughly 1 year.

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The Planetary Society release
LightSail 2 Spacecraft Successfully Demonstrates Flight by Light

Years of computer simulations. Countless ground tests. They've all led up to now. The Planetary Society's crowdfunded LightSail 2 spacecraft is successfully raising its orbit solely on the power of sunlight.

Since unfurling the spacecraft's silver solar sail last week, mission managers have been optimizing the way the spacecraft orients itself during solar sailing. After a few tweaks, LightSail 2 began raising its orbit around the Earth. In the past 4 days, the spacecraft has raised its orbital high point, or apogee, by about 2 kilometers. The perigee, or low point of its orbit, has dropped by a similar amount, which is consistent with pre-flight expectations for the effects of atmospheric drag on the spacecraft. The mission team has confirmed the apogee increase can only be attributed to solar sailing, meaning LightSail 2 has successfully completed its primary goal of demonstrating flight by light for CubeSats.

"We're thrilled to announce mission success for LightSail 2," said LightSail program manager and Planetary Society chief scientist Bruce Betts. "Our criteria was to demonstrate controlled solar sailing in a CubeSat by changing the spacecraft's orbit using only the light pressure of the Sun, something that's never been done before. I'm enormously proud of this team. It's been a long road and we did it."

The milestone makes LightSail 2 the first spacecraft to use solar sailing for propulsion in Earth orbit, the first small spacecraft to demonstrate solar sailing, and just the second-ever solar sail spacecraft to successfully fly, following Japan's IKAROS, which launched in 2010. LightSail 2 is also the first crowdfunded spacecraft to successfully demonstrate a new form of propulsion.

"For The Planetary Society, this moment has been decades in the making," said Planetary Society CEO Bill Nye. "Carl Sagan talked about solar sailing when I was in his class in 1977. But the idea goes back at least to 1607, when Johannes Kepler noticed that comet tails must be created by energy from the Sun. The LightSail 2 mission is a game-changer for spaceflight and advancing space exploration."

On Monday (July 29), LightSail 2 sent home a new full-resolution image captured by its camera during solar sail deployment. The perspective is opposite to last week's full-resolution image and shows the sail more fully deployed. LightSail 2's aluminized Mylar sail shines against the blackness of space, with the Sun peeking through near a sail boom.

Above: This image was taken during the LightSail 2 sail deployment sequence on 23 July 2019 at 11:49 PDT (18:49 UTC). The sail is almost fully deployed here and appears warped near the edges due to the spacecraft's 185-degree fisheye camera lens. The image has been color corrected and some of the distortion has been removed. The Sun is visible at center, and pieces of spectraline, which were used to hold LightSail 2's solar panels closed, can be seen at 5 o'clock and 7 o'clock.

The mission team will continue raising LightSail 2's orbit for roughly a month, until the perigee decreases to the point where atmospheric drag overcomes the thrust from solar sailing. During the orbit-raising period, the team will continue optimizing the performance of the solar sail.

"We've been working since sail deployment to refine the way the spacecraft tracks the Sun," said LightSail 2 project manager Dave Spencer. "The team has done a great job getting us to the point where we can declare mission success. Moving ahead, we're going to continue working to tune the sail control performance and see how much we can raise apogee over time."

One such refinement involves LightSail 2's single momentum wheel, which rotates the spacecraft broadside and then edge-on to the Sun each orbit to turn the thrust from solar sailing on and off. Momentum wheels can "saturate," hitting predefined speed limits, after which they are no longer effective at rotating the spacecraft. Most spacecraft use chemical thrusters to desaturate momentum wheels; LightSail 2 relies on electromagnetic torque rods, which orient the spacecraft by pushing against Earth's magnetic field.

LightSail 2's momentum wheel currently reaches its saturation limit a couple of times per day, and desaturating the wheel temporarily takes the spacecraft out of its proper orientation for solar sailing. The mission team already applied a software update that increased the time between saturation events, and is also working to automate the desaturation process. Both refinements should result in improved solar sailing performance.

Above: This chart shows LightSail 2's orbit apogee and perigee since launch. From 26 July to 30 July, the spacecraft raised its orbital high point, or apogee, by about 2 kilometers. A PDF version of this chart is available.

After LightSail 2's month-long orbit raising phase, the spacecraft will begin to deorbit, eventually reentering the atmosphere in roughly a year. The aluminized Mylar sail, about the size of a boxing ring, may currently be visible for some observers at dusk and dawn. The Planetary Society's mission control dashboard shows upcoming passes based on user location, and includes a link to a page that highlights passes when the sail is more likely to be visible.

Roughly 50,000 Planetary Society members and private citizens from more than 100 countries, as well as foundations and corporate partners, donated to the LightSail 2 mission, which cost $7 million from 2009 through March 2019.

"LightSail 2 proves the power of public support," said Planetary Society COO Jennifer Vaughn. "This moment could mark a paradigm shift that opens up space exploration to more players. It amazes me that 50,000 people came together to fly a solar sail. Imagine if that number became 500,000 or 5 million. It's a thrilling concept."

The Planetary Society shares LightSail program data with other organizations so that solar sail technology can be applied to future space exploration missions. The Society presented initial LightSail 2 results this week at the 5th International Symposium on Solar Sailing in Aachen, Germany. Results are also being shared with NASA's NEA Scout mission, which is launching a solar sail-powered CubeSat to visit a near-Earth asteroid as early as next year.

LightSail 2 is one of several Planetary Society science and technology projects that aim to advance space science and exploration. Earlier this month, NASA chose PlanetVac, a Society-funded technology built by Honeybee Robotics that simplifies the process of collecting samples from other worlds, to fly to the Moon as part of the agency's Commercial Lunar Payload Services (CLPS) program.

The LightSail program began in 2009 under the direction of Planetary Society co-founder Louis Friedman, following the launch of Cosmos 1, the world's first solar sail that did not reach orbit. Friedman and Society co-founders Carl Sagan and Bruce Murray championed the idea of solar sailing more than 4 decades ago with a proposed solar sail mission to Halley's Comet.

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The Planetary Society release
LightSail 2 Enters Extended Mission Phase

One year after launching into space, The Planetary Society's LightSail 2 spacecraft has completed its primary mission phase and is embarking on an extended mission dedicated to further advancing solar sailing technology.

The loaf-of-bread-sized spacecraft launched aboard a SpaceX Falcon Heavy rocket on 25 June 2019. One month later, it deployed an aluminized Mylar solar sail the size of a boxing ring and used sunlight alone to change its orbit, demonstrating the feasibility of controlled solar sailing for small spacecraft. While sunlight has no mass, it has momentum that can be harnessed for propulsion.

During the past year, the LightSail 2 mission team has continued to optimize the spacecraft's performance and report their results to the space science community. The Planetary Society will now operate LightSail 2 under an extended mission phase, making various operational refinements and studying how the spacecraft's orbit evolves in response.

"We've learned a lot about solar sailing over the past year, and LightSail 2 still has a lot to teach us," said Planetary Society chief scientist and LightSail 2 program manager Bruce Betts. "During our extended mission we'll continue making changes to our sail control software, which will help future solar sail missions optimize their performance. We also plan to test using the sail to intentionally generate additional atmospheric drag, which is a way in which future spacecraft could deorbit themselves, cutting down on the ever-growing amount of space debris."

LightSail 2's average orbital altitude — now roughly 707 kilometers (439 miles) — is slowly decreasing. Though the spacecraft orbits Earth higher than the International Space Station, the planet's atmosphere is still thick enough to counteract the thrust gained from solar sailing. Analyses of orbital data show that LightSail 2's rate of orbital decay is markedly slower in solar sailing mode, when the craft actively positions itself to get a push from sunlight. During some time intervals, the spacecraft even gains enough thrust to briefly overcome atmospheric drag and raise its orbit.

"The LightSail 2 flight team has done tremendous work over the past year to optimize the spacecraft performance and understand how the orbit is evolving," said David Spencer, the LightSail 2 project manager. "It's a challenge to orient a large, flexible solar sail in space, and the data collected during our primary and extended missions will provide critical advancements in solar sailing technology."

After a year in space, LightSail 2 remains healthy, except for a few minor problems. Images show one of the tape measure-like sail booms has buckled, and an analysis of shadows from the spacecraft's solar panels shows that one panel is not fully deployed. Neither of these issues has greatly impacted LightSail 2's solar sailing performance, nor have there been major impacts from the ongoing COVID-19 pandemic, since team members can operate the spacecraft remotely.

The LightSail 2 extended mission is expected to continue as long as the spacecraft remains healthy, or until its orbit decays and the spacecraft reenters Earth's atmosphere many months from now.

Results from LightSail program are being used to inform other solar sail missions, including NASA's NEA Scout, which will hitch a ride to lunar orbit aboard the first Space Launch System and Orion flight scheduled for next year. NEA Scout will use a solar sail to leave the vicinity of the Moon and visit a near-Earth asteroid. The Planetary Society shares LightSail data with NASA through a Space Act Agreement.

Extended mission goals

The LightSail 2 extended mission begins on 25 June 2020. Specific goals include:

  • Continue to tune LightSail 2's solar sail performance

  • Learn more about solar sailing operation through the study of various operational refinements and orbital evolution in response to sail control

  • Continue taking pictures for public outreach and engineering analyses, including to study sail, boom, and spacecraft evolution

  • Implement deorbit studies of sail dynamics with the sail acting as a drag sail

  • Test a ground-based fault protection algorithm being developed by Purdue University Ph.D. student Justin Mansell

  • Continue to share information about the mission and what we are learning from it with the technical community and the public, through peer-reviewed journal articles, conference presentations, direct contact with future solar sailing missions, web articles, and social media

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