LightSail 1 Mission Results and Public Outreach Strategies

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1 LightSail 1 Mission Results and Public Outreach Strategies By Bruce BETTS 1), Bill NYE 1), Jennifer VAUGHN 1), Erin GREESON 1), Richard CHUTE 1), David A. SPENCER 2), Rex W. RIDENOURE 3), Riki MUNAKATA 3), Stephanie D. WONG 3), Alex DIAZ 3), Douglas A. STETSON 4), Justin D. FOLEY 5), John M. BELLARDO 5), and Barbara A. PLANTE 6) 1) The Planetary Society, 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 solar sail 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 Bill Nye, 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 Carl Sagan 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, Planetary Radio, social media, and print materials; and (8) Special events both physical at launch, and virtual. Key Words: Solar Sailing, CubeSat, Outreach 1. Introduction In 2009, The Planetary Society initiated the LightSail program to advance the maturity of solar sailing technology using the 3U CubeSat platform. 1) The LightSail 1 mission was designed to provide on-orbit validation of the CubeSat functionality and demonstrate sail deployment in low-earth orbit, while the subsequent LightSail 2 mission would demonstrate sail control in order to raise orbit apogee. LightSail 1 was competitively awarded a launch slot as a secondary payload through NASA s Educational Launch of Nanosatellites (ELaNa) program. Following a five-year development, LightSail 1 launched as part of the ULTRASat payload on an Atlas V launch vehicle on May 20, LightSail 1 was the third solar sailing mission to successfully launch, achieve sail deployment, and operate in space. In May 2010, the Japanese space agency JAXA launched a mission to Venus with a secondary payload called Interplanetary Kitecraft Accelerated by Radiation Of the Sun (IKAROS). Three weeks after launch, IKAROS was successfully deployed and became the first-ever solar sailing demonstrator. 2) Subsequently, NASA launched the NanoSail-D2 on board the FASTSAT spacecraft in November Following a delayed deployment from FASTSAT, NanoSail-D2 deployed a 10 m 2 solar sail from a 3U CubeSat. 3) The LightSail program was structured to build on these successes, demonstrating a controllable solar sail for the in-space propulsion of CubeSat platforms. Founded in 1980, The Planetary Society is the world s largest and most influential public space organization group, with more than 40,000 active members. With a charter to inspire and involve the world's public in space exploration through advocacy, projects, and education, 4) The Planetary Society crafted a public outreach campaign centered on the LightSail program (Fig. 1). In this paper, the LightSail 1 mission results are presented. A summary of the LightSail spacecraft design is provided in Section 2, and the on-orbit performance of the LightSail 1 spacecraft is evaluated in Section 3. Anomalies encountered during the mission are described, along with the flight team s anomaly response actions. In Section 4, the LightSail public outreach campaign is described. The planned LightSail 2 mission is described in a separate paper. 5) 1

2. LightSail Spacecraft Design The LightSail spacecraft design adopted the 3U CubeSat standard in order to leverage a growing vendor supply chain of off-the-shelf spacecraft components, and

The solar sail assembly occupies 2U, partitioned into the sail storage section and the sail motor/boom drive assembly.

2 2. LightSail Spacecraft Design The LightSail spacecraft design adopted the 3U CubeSat standard in order to leverage a growing vendor supply chain of off-the-shelf spacecraft components, and assemblies that facilitate flight system integration. In the LightSail CubeSat design, a 1U volume is reserved for the avionics section, which has hinges for four full-length deployable solar panels. The solar sail assembly occupies 2U, partitioned into the sail storage section and the sail motor/boom drive assembly. LightSail is designed for deployment from a Poly-Picosatellite Orbital Deployer (P-POD). Four side-mounted solar panels are deployable, and a deployable monopole antenna is used for RF communications. The avionics section houses two processor boards, a radio, 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. and manages deployments as directed by the avionics board. Four independent triangular aluminized Mylar sail sections 4.6 microns thick are Z-folded and stowed in the four sail bays at the spacecraft midsection. Fig. 2 shows LightSail 1 in a partially deployed state, with two solar panels fully deployed, two partly deployed and two bays with folded sail underneath. Each sail section is attached to a 4-m Triangular Retractable And Collapsible (TRAC) boom made of elgiloy, a nonmagnetic non-corrosive alloy; these booms are wound around a common spindle driven by a Faulhaber motor containing Hall sensors. The sail system is deployed when FSW initializes the motor and then commands a prescribed number of motor counts to extend the sail sections to their desired positions. Fully deployed, the square sail is about 8 m on the diagonal, with a total sail area of 32 m 2. 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, The launch vehicle targeted orbit altitudes of 356 km x 705 km, with an orbital inclination 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 2

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.

The stations were networked to a telemetry database server at Cal Poly, and commanded by operators at terminals at Cal Poly and Georgia Tech.

3 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 California Polytechnic University, San Luis Obispo (Cal Poly) and Georgia Institute of Technology (Georgia Tech). The stations were networked to a telemetry database server at Cal Poly, and commanded by operators at terminals at Cal Poly and Georgia Tech. The Cal Poly station utilized a dualphased Yagi antenna connected to an amateur satellite radio, which was then connected to a computer to encode and decode telemetry. The computer also gimbals the antenna to point at satellites as they pass overhead. Georgia Tech used a single Yagi antenna connected to nearly identical radio and encoding/decoding equipment. Initial acquisition of the downlink signal was received by the Cal Poly tracking station on schedule, 75 minutes after P- POD ejection (Fig. 4). Telemetry data, in the form of 220- Byte beacon packets of engineering data transmitted every 15 seconds, were received during the first two planned back-toback tracking passes over Cal Poly and Georgia Tech. Receipt of this initial data set confirmed that the RF antenna deployment event occurred as sequenced, batteries were charged, and attitude rates were within the expected ranges. A solar panel deployment indicator switch indicated that all panels were in the deployed configuration, which was unexpected, however, the switch was presumed to have triggered due to easing of the solar panel retention lines due to the launch vibration environment (a similar spurious panel deployment switch reading occurred during a LightSail 1 vibration test). Nine successful tracking passes were completed during the first 24 hours of the mission, and the spacecraft capability to receive ground commands was validated via a command to turn off rate gyros. Two days after launch, it was noticed that a file in the onboard file system was rapidly growing in size. There was concern that the Linux system could crash due to a file size overload. Just before the next planned tracking station overflight, before the flight team could take action, the board did indeed crash. LightSail 1 fell completely silent for days, in spite of the operations team sending reboot commands during dozens of passes over Cal Poly and Georgia Tech. (Hardware- and software-based watchdog timers in the Intrepid board were not functional for LightSail 1.) Eight days later, a spontaneous system reboot occurred, presumably due to a radiation-induced charged particle impact. The spacecraft resumed downlinking telemetry beacons, and the flight team initiated procedures to prevent future file system overloads. For the remainder of the mission, the file write volume vulnerability was managed via commanded reboots. Commands tasking each camera to acquire test images successfully implemented, and images from the stowed configuration were downlinked over the next two days (Fig. 5). The sunlight penetration in the on-orbit image confirmed suspicions that the solar panel restraining lines had loosened slightly during the launch and/or P-POD deployment phase, resulting in the spurious deployment switch readings indicating that the panels were deployed. The image confirmed that the camera was functioning properly, and it also provided positive confirmation that the solar panels were in the stowed configuration. 3

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.

4 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. configuration. Test image acquired of the spacecraft interior in the stowed 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 batteries were likely in a fault condition stemming from the solar panel deployment event. The flight team discussed the option of commanding an emergency solar sail deployment, but all ground testing of the solar sail deployment sequence had been performed under battery power, with all battery cells online and fully charged. It was uncertain whether the sail deployment could be successfully completed without battery power, relying only upon direct input from the solar panels. The flight team decided to address the electrical power subsystem anomaly first, and approach solar sail deployment in a known state consistent with ground testing, if possible. Sail deployment was deferred pending investigation of the electrical power subsystem anomaly. However, during the next three days, no beacons were received from LightSail 1. On June 6, contact was regained with the spacecraft, and telemetry indicated that the batteries were charging when in sunlight. The battery circuitry behavior was anomalous, resulting in periods where the spacecraft was not drawing battery power. Telemetry from the first June 7 tracking pass was nominal, with good power levels and the batteries discharging as expected, so the team elected to command sail deployment. During the final tracking pass on June 7, controllers at Cal Poly sent the command to deploy the solar sail. The deployment command was successfully executed, and the sail motor began deploying the booms. Over two minutes of motor count telemetry were received, indicating that the motors were driving the sail booms out at a rate consistent with ground testing. Telemetry from the June 8 tracking passes showed that gyro rates had dropped to nearly zero, another indication of a Fig. 6. Image of the deployed LightSail 1 solar sail. On June 11, LightSail 1 entered an anomalous mode of continuous transmission of RF noise. Ground controllers were unable to recover from this anomalous condition. LightSail 1 re-entered the atmosphere and burned up off the east coast of Argentina over the Falkland Islands on the morning of June 14, seven days after sail deployment. 4. LightSail 1 Public Outreach The LightSail 1 mission was not only a technical success, but also a success in exciting, inspiring, and engaging the public in the mission. 7) The Planetary Society s mission is to empower the world s citizens to advance space science and exploration. Through its LightSail program, it seeks to not only provide a successful demonstration of solar sailing in the context of CubeSat missions, but also seeks to engage and excite the public. LightSail 1 s public outreach included the following elements: (1) Inspiring Spokespeople - well known spokespeople included CEO Bill Nye, as well as Board Member Neil degrasse Tyson discussing how citizens could join LightSail s journey; (2) Good timing - The Planetary Society identified January 2015 as an excellent time to publicize LightSail 1 in the context of other space events (3) Science Education - reporter Jason Davis was embedded with the LightSail technical team, enabling transparent coverage for the public and educational information. (4) Historical storytelling - footage of co-founder Carl Sagan discussing solar sailing with Johnny Carson on a 1976 episode of The Tonight Show was paired with LightSail described by present leader, Bill Nye; (5) Public Engagement Campaigns 4

5 - 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 - a LightSail Kickstarter expanded the citizen-funded aspect of the mission attracting 23,500 backers who gave $1.3M USD; (7) Multimedia resources included a web microsite, videos, animations, Planetary Radio, social media, and print materials; (8) Special events most notably LightSail 1 s successful launch from Cape Canaveral allowed onsite opportunities for people to join The Planetary Society leaders and staff; (9) Virtual Events - people also celebrated virtually, through social media and The Planetary Society global volunteer network; and (10) Inclusive Messaging-themes were citizen-funded and democratization of space. LightSail 1 goals for public outreach were exceeded, and the multi-pronged outreach approach for LightSail 1 engaged the public, and demonstrated strong public interest in missions like LightSail 1. We look forward, through similar efforts, to engaging the public with LightSail Conclusion As a precursor mission, the primary goals of LightSail 1 were to provide on-orbit validation of flight system performance, successfully deploy the solar sail, and downlink images showing the sail in the deployed configuration. The flight team overcame numerous challenges in meeting each of these mission objectives. Lessons learned during onorbit operations were documented and have been systematically addressed for LightSail 2 mission, leading to a 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. campaign contributors, who supported the LightSail program development and operations. LightSail 1 would not have succeeded without their support. We also thank the numerous members of the amateur radio community and amateur astronomers who contributed their time and effort to assist LightSail 1 operations. References 1) Ridenoure, R.W., Spencer, D.A., Stetson, D.A., Betts, B., Munakata, R., Wong, S.D., Diaz, A., Plante, B.A., Foley, J.D., and Bellardo, J.M.: The LightSail Program: Advancing Solar Sailing Technology Using a CubeSat Platform, Journal of Small Satellites, Vol 5, No. 3, October ) Space.com (June 11, 2010): Japanese Spacecraft Deploys Solar Sail, Available at: japanese-spacecraft-deploys-solar-sail.html (Accessed June 12, 2016). 3) Alhorn, D., Casas, J., Agasid, E.F., Adams, C.L., Laue, G., Kitts, C.,: NanoSail-D: The Small Satellite That Could!, Paper SSC11-VI-1, 2011 Conference on Small Satellites, Logan, Utah, ) The Planetary Society, 5) Betts, B., Spencer, D., Nye, B., Munakata, R., Bellardo, J.M., Wong, S.D., Diaz, A., Ridenoure, R.W., Plante, B.L., Foley, J.D., Vaughn, J.: LightSail 2: Controlled Solar Sailing Using a CubeSat, 4 th International Solar Sailing Symposium, Kyoto, Japan, January ) Ray, J.: X-37B Spaceplane Embarks On Fourth Voyage In Orbit, SpaceflightNow.com, (Accessed June 12, 2016). 7) Nye, B., Greeson, E.: The LightSail Story, Public Outreach Strategies & Results, Proceedings 67th International Astronautical Congress, E1.6, Acknowledgments The authors would like to acknowledge the donors and members of The Planetary Society, and the Kickstarter 5

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