Micro Fabricated Optical Seismometer "FROSTY"

Michigan Aerospace Corporation has assembled a team to develop a Micro Fabricated Optical Seismometer “FROSTY” based on whispering gallery mode technology. The concept, already verified using meso-scale components, will be developed for the demanding conditions found on Europa and other planetary bodies of our solar system (and beyond). For Europa in particular, this sensor will allow surface-based measurements of ice crust thickness and seismic activity. Planetary exploration presents considerable challenges to the hardware. The average temperature on Europa is 90K (140K at the equator near dark material during daytime and near 50K at the poles) and radiation near 540 rem per day as Europa orbits within Jupiter's radiation belts. This all-optical seismometer affords advantages over conventional instrumentation. The proposed seismometer will be compact and will require low power to operate. Communication between the seismometer and the attending electronics will be conducted using optical fibers, thus mitigating the impact of high radiation characteristic of planetary exploration. The silicon-based monolithic fabrication will ensure that the instrument is able to withstand the rigor of space travel. In the proposed concept, optical whispering gallery modes (WGM), also known as morphology dependent resonances (MDR), are used to measure minute variations in the resonances of an optical micro-resonator affected by the motion of a proof mass. These resonances afford a very high optical quality factor Q, greater than 10^6. Due to the high Q-factors, the linewidths of these resonances can be extremely narrow, making them highly sensitive to any change in the morphology (shape, size, index of refraction) of the resonator or its immediate surroundings (proof mass in this case). The micro-fabrication techniques will entail silicon photolithography, E-beam lithography and deep reactive ion etching (DRIE) for precise positioning of the components. The proposed effort will extend over two years. The first year will entail the fabrication and testing of the optical resonator, and the completion of the seismometer. The second year will see the fabrication and testing of the seismometer. Because of the low SWaP, such a seismometer will be suitable for NASA's robotic missions. The entry TRL is 2 and exit TRL is 4. More »