Planetary Radio Extra: LightSail Update

Episode Summary

Executive Summary: This Planetary Radio Extra focuses on LightSail 2, The Planetary Society’s solar-sailing CubeSat mission. Bruce Betts and Jason Davis explain the spacecraft’s redesign, intensive testing, and upcoming steps toward launch aboard SpaceX’s Falcon Heavy, emphasizing that thorough ground testing is essential to uncover and fix problems before flight.

Main Topics: What LightSail is and why it matters: Bruce explains solar sailing as using sunlight pressure for propulsion, enabling spacecraft to change orbit without fuel and potentially support future interplanetary missions. LightSail 2 upgrades and software overhaul: Jason describes how nearly every subsystem has been touched, with major software improvements and added telemetry to improve visibility and reliability. Operational Readiness Test (ORT) and BenchSat simulation: The team rehearses spacecraft operations with a clone called BenchSat, simulating ground contacts, subsystem reviews, and deployment sequences to validate procedures and software. Deployment testing and boom/sail mechanics: The sail deployment test confirmed the main deployment sequence while exposing minor issues; the booms extend the Mylar sail using custom motors and retractable logic. Mission integration with Prox-1 and launch plan: After successful testing, LightSail 2 is expected to be integrated inside Georgia Tech’s Prox-1 spacecraft and launched on a Falcon Heavy mission. Public outreach, tracking, and mission coverage: The team plans continued blog updates, amateur radio packet reception, and a real-time telemetry dashboard so the public can follow the mission.

Key Arguments: Solar sailing is a viable propulsion technique because light exerts measurable pressure on a reflective sail in space. The spacecraft must be tested exhaustively on Earth because repairs in orbit are effectively impossible. Software revisions are crucial: LightSail 2 has significantly more telemetry than LightSail 1, improving diagnostics and mission control. BenchSat and ORT procedures allow the team to practice the exact mission workflow, revealing both software bugs and procedural issues before launch. The deployment test was successful in that the sail and booms deployed, but small glitches are expected and should be resolved through iterative testing. Integration with Prox-1 will change the mission architecture by nesting LightSail inside another spacecraft before release in orbit.

Data Points: Spacecraft mass: 5 kilograms - Bruce describes LightSail 2 as a small CubeSat roughly the size of a loaf of bread. CubeSat size: 3U CubeSat - LightSail 2 is built in a standard CubeSat form factor. First mission telemetry lines: about 80 odd lines - Jason compares telemetry capacity from the first LightSail mission to the second. Telemetry increase: almost tripled - Software upgrades significantly expanded onboard telemetry for LightSail 2. Boom length: 4 meters - Each boom extends out to this length during sail deployment. Deployment duration: a couple minutes - The booms are extended by a custom motor over this period. Motor counter peak: about 134,000 - Jason notes the telemetry count reached this value during the deployment test, matching the prior space deployment. Launch vehicle: SpaceX Falcon Heavy - PROX-1 with LightSail 2 is slated to launch on Falcon Heavy's second flight. Launch window: September 2016 - Bruce says the mission is officially scheduled for September, though delays may shift it. Testing milestone timing: roughly mid-late March - Bruce estimates the Day-in-the-Life test timeframe.

Pivotal Quotes: "We're finding problems, which can be disturbing, but on the other hand, it's exactly why you're testing." — Bruce Betts: Bruce explains the value of the ongoing integration and deployment tests. "The sail deployed, but there were several minor glitches." — Bruce Betts: Bruce summarizes the outcome of the deployment test and the need for follow-up fixes. "It's all got to get up into orbit first." — Bruce Betts: Bruce highlights the dependency on a successful launch before any in-space demonstration can occur.

Implications: LightSail 2 shows how small, low-cost spacecraft can mature through disciplined testing, potentially proving sunlight-driven propulsion for future deep-space missions and expanding public participation in mission tracking.