Vibration analysis and testing for the LLST optical module

Abstract

A lunar orbiting space terminal was recently developed as part of NASA’s Lunar Laser Communications Demonstration program. The space terminal uses a 10 centimeter, inertially-stabilized telescope and a 0.5 watt beam to transmit data at up to 622Mbps between the Moon and one of several ground terminals on Earth. Tight coupling between analysis and testing was used to ensure both performance and survival requirements were met in the operational and non-operational vibration environments. Performance requirements were driven by the need to meet a 4.2 μrad pointing stability requirement in the operational vibration environment. A highly-correlated FEA model was developed using vibration testing to extrapolate the behavior of the system beyond the practical limits of the vibration test bed. The launch load non-operational vibration environment was simulated through both analysis and testing using force-limiting to avoid over designing and over testing the sensitive optics. The iterative and associated challenges of the vibration analysis and testing effort are discussed to show how those efforts helped enable the successful launch, deployment, and ultimately demonstration of NASA’s first space laser communications program.