LightSail 1 Mission Results and Public Outreach Strategies

By Bruce BETTS1), Bill NYE1), Jennifer VAUGHN1), Erin GREESON1), Richard CHUTE1), David A. SPENCER2), Rex W. RIDENOURE3), Riki MUNAKATA3), Stephanie D. WONG3), Alex DIAZ3), Douglas A. STETSON4), Justin D. FOLEY5), John M. BELLARDO5), and Barbara A. PLANTE6)

1), Pasadena, California, USA 2)School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA 3)Ecliptic Enterprises Corporation, Pasadena, California, USA 4)Space Science and Exploration Consulting Group, Pasadena, California, USA 5)California Polytechnic State University, San Luis Obispo, California, USA 6)Boreal Space, Hayward, California, USA

Conceived by The Planetary Society, and funded by private donations, the LightSail program consists of two missions, LightSail 1 and LightSail 2, seeking to demonstrate controlled solar sailing using a 3U CubeSat spacecraft bus. This paper reports results of the LightSail 1 mission, a five-week 2015 mission in low Earth-orbit that successfully demonstrated the deployment approach. Once in orbit, the LightSail 1 mission operations team stepped through a two-week checkout period, with useful images and spacecraft performance data transmitted to two ground stations in the United States. Following resolution of several significant anomalies during the early phases of the mission, the LightSail 1 solar sail was successfully deployed. Following sail deployment, spacecraft subsystem testing was completed and an image showing the deployed sail was downlinked before the spacecraft re-entered the atmosphere. Through the LightSail program, The Planetary Society also seeks to engage and excite the public. LightSail 1’s public outreach strategy included: (1) Inspiring spokespeople, including The Planetary Society Chief Executive Officer , as well as board member Neil deGrasse Tyson; (2) Good choice of publicity timing; (3) Science education, including transparent regular coverage of the mission development and operations; (4) Historical storytelling - footage of co-founder discussing solar sailing with Johnny Carson on a 1976 episode of “The Tonight Show” paired with LightSail described by present leader, Bill Nye; (5) Public engagement campaigns - these included Selfies to Space, where the public was able to submit photos and/or names to ride on board LightSail 2; (6) a Kickstarter campaign that expanded the citizen-funded aspect of the mission attracting 23,500 backers who gave $1.3M USD; (7) Multimedia –web microsite, videos, animations, , social media, and print materials; and (8) Special events – both physical at launch, and virtual.

Key Words: Solar Sailing, CubeSat, Outreach

1. Introduction spacecraft in November 2010. Following a delayed deployment from FASTSAT, NanoSail-D2 deployed a 10 m2 In 2009, The Planetary Society initiated the LightSail solar sail from a 3U CubeSat.3) The LightSail program was program to advance the maturity of solar sailing technology structured to build on these successes, demonstrating a using the 3U CubeSat platform.1) The LightSail 1 mission was controllable solar sail for the in-space propulsion of CubeSat designed to provide on-orbit validation of the CubeSat platforms. functionality and demonstrate sail deployment in low-Earth Founded in 1980, The Planetary Society is the world’s largest orbit, while the subsequent LightSail 2 mission would and most influential public space organization group, with more demonstrate sail control in order to raise orbit apogee. than 40,000 active members. With a charter to “inspire and LightSail 1 was competitively awarded a launch slot as a involve the world's public in through secondary payload through NASA’s Educational Launch of advocacy, projects, and education,”4) The Planetary Society Nanosatellites (ELaNa) program. Following a five-year crafted a public outreach campaign centered on the LightSail development, LightSail 1 launched as part of the ULTRASat program (Fig. 1). payload on an Atlas V launch vehicle on May 20, 2015. In this paper, the LightSail 1 mission results are presented. LightSail 1 was the third solar sailing mission to successfully A summary of the LightSail spacecraft design is provided in launch, achieve sail deployment, and operate in space. In May Section 2, and the on-orbit performance of the LightSail 1 2010, the Japanese space agency JAXA launched a mission to spacecraft is evaluated in Section 3. Anomalies encountered Venus with a secondary payload called Interplanetary Kite- during the mission are described, along with the flight team’s craft Accelerated by Radiation Of the Sun (IKAROS). Three anomaly response actions. In Section 4, the LightSail public weeks after launch, IKAROS was successfully deployed and outreach campaign is described. The planned LightSail 2 became the first-ever solar sailing demonstrator.2) Subsequently, mission is described in a separate paper.5) NASA launched the NanoSail-D2 on board the FASTSAT

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2. LightSail Spacecraft Design and manages deployments as directed by the avionics board. Four independent triangular aluminized Mylar® sail sections The LightSail spacecraft design adopted the 3U CubeSat 4.6 microns thick are Z-folded and stowed in the four sail bays standard in order to leverage a growing vendor supply chain of at the spacecraft midsection. Fig. 2 shows LightSail 1 in a off-the-shelf spacecraft components, and assemblies that partially deployed state, with two solar panels fully deployed, facilitate flight system integration. In the LightSail CubeSat two partly deployed and two bays with folded sail underneath. design, a 1U volume is reserved for the avionics section, which Each sail section is attached to a 4-m Triangular Retractable has hinges for four full-length deployable solar panels. The And Collapsible (TRAC) boom made of elgiloy, a non- solar sail assembly occupies 2U, partitioned into the sail storage magnetic non-corrosive alloy; these booms are wound around a section and the sail motor/boom drive assembly. LightSail is common spindle driven by a Faulhaber motor containing Hall designed for deployment from a Poly-Picosatellite Orbital sensors. The sail system is deployed when FSW initializes the Deployer (P-POD). Four side-mounted solar panels are motor and then commands a prescribed number of motor counts deployable, and a deployable monopole antenna is used for RF to extend the sail sections to their desired positions. Fully communications. deployed, the square sail is about 8 m on the diagonal, with a The avionics section houses two processor boards, a radio, total sail area of 32 m2. batteries, sensors and actuators, and associated harnessing. LightSail 1 was designed to utilize torque rods for attitude control, although a flight software error precluded on-orbit actuation of torque rods. Two small solar panels (one fixed at each end of the CubeSat) and four full-length deployable panels provide power and define the spacecraft exterior. The larger solar panels are in their stowed configuration until either autonomously commanded by onboard software or manually commanded from the ground. With solar cells populating both sides of each large panel, they generate power whether in the stowed or deployed configuration. However, the panels must be deployed before solar sail deployment. Deployment of all four deployable solar panels is accomplished with a common burn-wire assembly mounted near the RF antenna assembly. Each solar panel carries Sun sensors, magnetometers, power sensors and temperature sensors. Two opposing large solar panels are equipped with cameras for imaging sail deployment.

Fig. 2. LightSail 1 engineer Alex Diaz showing the folded solar sail segments in the payload bays.

3. LightSail 1 Mission Operations

The Atlas 5 launch carrying the X-37B spaceplane and the ULTRASat payload including LightSail 1 occurred on May 20, 2015. The launch vehicle targeted orbit altitudes of 356 km x 705 km, with an of 55°.6) The last of the eight ULTRASat P-PODs to be actuated, LightSail 1 was deployed into orbit two hours after launch.

Fig. 1. The Planetary Society Chief Executive Officer Bill Nye with a full-scale engineering-model of the LightSail 3U CubeSat.

The spacecraft is controlled by flight software (FSW) that allocates functionality to two different processor boards. The main avionics board is tasked with spacecraft commanding, data collection, telemetry downlink, power management and initiating deployments. The payload interface board (PIB) integrates sensor data for attitude control, commands actuators

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Fig. 3. LightSail 1 was integrated with the flight P-POD (left), which was configured as part of the ULTRASat payload (right).

Fig. 4. Cal Poly ground station antennas tracking LightSail 1.

LightSail 1 was controlled from ground stations located at validated via a command to turn off rate gyros. California Polytechnic University, San Luis Obispo (Cal Two days after launch, it was noticed that a file in the Poly) and Georgia Institute of Technology (Georgia Tech). onboard file system was rapidly growing in size. There was The stations were networked to a telemetry database server at concern that the Linux system could crash due to a file size Cal Poly, and commanded by operators at terminals at Cal overload. Just before the next planned tracking station Poly and Georgia Tech. The Cal Poly station utilized a dual- overflight, before the flight team could take action, the board phased Yagi antenna connected to an amateur satellite radio, did indeed crash. LightSail 1 fell completely silent for days, which was then connected to a computer to encode and in spite of the operations team sending reboot commands decode telemetry. The computer also gimbals the antenna to during dozens of passes over Cal Poly and Georgia Tech. point at satellites as they pass overhead. Georgia Tech used a (Hardware- and software-based watchdog timers in the single Yagi antenna connected to nearly identical radio and Intrepid board were not functional for LightSail 1.) Eight encoding/decoding equipment. days later, a spontaneous system reboot occurred, presumably Initial acquisition of the downlink signal was received by due to a radiation-induced charged particle impact. The the Cal Poly tracking station on schedule, 75 minutes after P- spacecraft resumed downlinking telemetry beacons, and the POD ejection (Fig. 4). Telemetry data, in the form of 220- flight team initiated procedures to prevent future file system Byte beacon packets of engineering data transmitted every 15 overloads. For the remainder of the mission, the file write seconds, were received during the first two planned back-to- volume vulnerability was managed via commanded reboots. back tracking passes over Cal Poly and Georgia Tech. Commands tasking each camera to acquire test images Receipt of this initial data set confirmed that the RF antenna successfully implemented, and images from the stowed deployment event occurred as sequenced, batteries were configuration were downlinked over the next two days (Fig. charged, and attitude rates were within the expected ranges. 5). The sunlight penetration in the on-orbit image confirmed A solar panel deployment indicator switch indicated that all suspicions that the solar panel restraining lines had loosened panels were in the deployed configuration, which was slightly during the launch and/or P-POD deployment phase, unexpected, however, the switch was presumed to have resulting in the spurious deployment switch readings triggered due to easing of the solar panel retention lines due indicating that the panels were deployed. The image to the launch vibration environment (a similar spurious panel confirmed that the camera was functioning properly, and it deployment switch reading occurred during a LightSail 1 also provided positive confirmation that the solar panels were vibration test). Nine successful tracking passes were in the stowed configuration. completed during the first 24 hours of the mission, and the spacecraft capability to receive ground commands was

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successful sail deployment. All other subsystems were nominal. The team spent June 8 stepping through the command sequences to transfer the stored deployment images from the camera memories into the Intrepid board’s memory, and then downlink one full image to the ground. The image, shown in Fig. 6, revealed a deployed solar sail, with the sun in the background. A portion of the sail material appears to be wrapped over a boom tip. With all primary mission objectives accomplished, the LightSail 1 mission was declared a success on the afternoon of June 9.

Fig. 5. Test image acquired of the spacecraft interior in the stowed configuration.

Solar panel deployment commands were sent on June 3, and subsequent beacon packets indicated successful deployment based upon the gyro rate data, solar panel temperatures (colder) and sun sensor data. Several hours after solar panel deployment, telemetry indicated that all eight batteries were close to their nominal charge levels but the batteries were not connected to the main power bus. Current was neither flowing into nor out of the batteries. This indicated that all Fig. 6. Image of the deployed LightSail 1 solar sail. batteries were likely in a fault condition stemming from the solar panel deployment event. On June 11, LightSail 1 entered an anomalous mode of The flight team discussed the option of commanding an continuous transmission of RF noise. Ground controllers emergency solar sail deployment, but all ground testing of the were unable to recover from this anomalous condition. solar sail deployment sequence had been performed under LightSail 1 re-entered the atmosphere and burned up off the battery power, with all battery cells online and fully charged. east coast of Argentina over the Falkland Islands on the It was uncertain whether the sail deployment could be morning of June 14, seven days after sail deployment. successfully completed without battery power, relying only upon direct input from the solar panels. The flight team 4. LightSail 1 Public Outreach decided to address the electrical power subsystem anomaly first, and approach solar sail deployment in a known state The LightSail 1 mission was not only a technical success, consistent with ground testing, if possible. Sail deployment but also a success in exciting, inspiring, and engaging the was deferred pending investigation of the electrical power public in the mission.7) The Planetary Society’s mission is subsystem anomaly. to empower the world’s citizens to advance space science and However, during the next three days, no beacons were exploration. Through its LightSail program, it seeks to not received from LightSail 1. On June 6, contact was regained only provide a successful demonstration of solar sailing in the with the spacecraft, and telemetry indicated that the batteries context of CubeSat missions, but also seeks to engage and were charging when in sunlight. The battery circuitry excite the public. behavior was anomalous, resulting in periods where the LightSail 1’s public outreach included the following spacecraft was not drawing battery power. elements: (1) Inspiring Spokespeople - well known Telemetry from the first June 7 tracking pass was nominal, spokespeople included CEO Bill Nye, as well as Board with good power levels and the batteries discharging as Member Neil deGrasse Tyson discussing how citizens could expected, so the team elected to command sail deployment. join LightSail’s journey; (2) Good timing - The Planetary During the final tracking pass on June 7, controllers at Cal Society identified January 2015 as an excellent time to Poly sent the command to deploy the solar sail. The publicize LightSail 1 in the context of other space events (3) deployment command was successfully executed, and the sail Science Education - reporter Jason Davis was embedded with motor began deploying the booms. Over two minutes of the LightSail technical team, enabling transparent coverage motor count telemetry were received, indicating that the for the public and educational information. (4) Historical motors were driving the sail booms out at a rate consistent storytelling - footage of co-founder Carl Sagan discussing with ground testing. solar sailing with Johnny Carson on a 1976 episode of “The Telemetry from the June 8 tracking passes showed that Tonight Show” was paired with LightSail described by gyro rates had dropped to nearly zero, another indication of a present leader, Bill Nye; (5) Public Engagement Campaigns

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- these included Selfies to Space, where the public was able campaign contributors, who supported the LightSail program to submit photos and/or names to ride on board LightSail 2; development and operations. LightSail 1 would not have (6) a Kickstarter Campaign - a LightSail Kickstarter succeeded without their support. We also thank the expanded the citizen-funded aspect of the mission attracting numerous members of the amateur radio community and 23,500 backers who gave $1.3M USD; (7) Multimedia – amateur astronomers who contributed their time and effort to resources included a web microsite, videos, animations, assist LightSail 1 operations. Planetary Radio, social media, and print materials; (8) Special events – most notably LightSail 1’s successful launch from References Cape Canaveral allowed onsite opportunities for people to 1) Ridenoure, R.W., Spencer, D.A., Stetson, D.A., Betts, B., join The Planetary Society leaders and staff; (9) Virtual Munakata, R., Wong, S.D., Diaz, A., Plante, B.A., Foley, J.D., and Bellardo, J.M.: The LightSail Program: Advancing Solar Events - people also celebrated virtually, through social Sailing Technology Using a CubeSat Platform, Journal of Small media and The Planetary Society global volunteer network; Satellites, Vol 5, No. 3, October 2016. and (10) Inclusive Messaging-themes were “citizen-funded” 2) Space.com (June 11, 2010): “Japanese Spacecraft Deploys and “democratization of space.” Solar Sail,” Available at: http://www.space.com/8584- japanese-spacecraft-deploys-solar-sail.html (Accessed June 12, LightSail 1 goals for public outreach were exceeded, and 2016). the multi-pronged outreach approach for LightSail 1 engaged 3) Alhorn, D., Casas, J., Agasid, E.F., Adams, C.L., Laue, G., the public, and demonstrated strong public interest in Kitts, C.,: NanoSail-D: The Small Satellite That Could!, Paper SSC11-VI-1, 2011 Conference on Small Satellites, missions like LightSail 1. We look forward, through similar Logan, Utah, 2011. efforts, to engaging the public with LightSail 2. 4) The Planetary Society, http://www.planetary.org/about/. 5) Betts, B., Spencer, D., Nye, B., Munakata, R., Bellardo, J.M., 5. Conclusion Wong, S.D., Diaz, A., Ridenoure, R.W., Plante, B.L., Foley, J.D., Vaughn, J.: LightSail 2: Controlled Solar Sailing Using a CubeSat, 4th International Solar Sailing Symposium, Kyoto, As a precursor mission, the primary goals of LightSail 1 Japan, January 2017. were to provide on-orbit validation of flight system 6) Ray, J.: “X-37B Spaceplane Embarks On Fourth Voyage In performance, successfully deploy the solar sail, and downlink Orbit,” SpaceflightNow.com, images showing the sail in the deployed configuration. The http://spaceflightnow.com/2015/05/20/recap-story-x-37b- flight team overcame numerous challenges in meeting each embarks-on-fourth-voyage-in-space/, (Accessed June 12, 2016). of these mission objectives. Lessons learned during on- 7) Nye, B., Greeson, E.: The LightSail Story, Public Outreach orbit operations were documented and have been Strategies & Results, Proceedings 67th International systematically addressed for LightSail 2 mission, leading to a Astronautical Congress, E1.6, 2016. lower risk posture for the follow-on mission. Through a carefully orchestrated public outreach strategy, the interest and public engagement generated by the LightSail 1 mission and the associated outreach activities exceeded expectations. The program’s transparent approach, sharing the challenges and setbacks that the engineering and management team grappled with during development and operations, clearly resonated with the public and built support for the mission. The exceptionally strong Kickstarter campaign shows that there is broad support for ambitious, high-risk, privately-funded small satellite missions that are working to advance the state of the art in key technology areas to enable space science.

Acknowledgments

The authors would like to acknowledge the donors and members of The Planetary Society, and the Kickstarter

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