Andreas Zoellner

UV LED charge control of an electrically isolated proof mass in a Gravitational Reference Sensor configuration at 255 nm

Data from a satellite mission will show that compact, low-power AlGaN Ultraviolet LEDs operating at 255 nm are effective for precise control of the potential of an electrically isolated proof mass with applications in gravitational reference sensors.

Differential optical shadow sensor for sub-nanometer displacement measurement and its application to drag-free satellites

We present a method for 3D sub-nanometer displacement measurement using a set of differential optical shadow sensors. It is based on using pairs of collimated beams on opposite sides of an object that are partially blocked by it. Applied to a sphere, our 3-axis sensor module consists of 8 parallel beam-detector sets for redundancy. The sphere blocks half of each beams power in the nominal centered position, and any displacement can be measured by the differential optical power changes amongst the pairs of detectors. We have experimentally demonstrated a displacement sensitivity of 0.87nm/Hz at 1 Hz and 0.39nm/Hz at 10 Hz. We describe the application of the module to the inertial sensor of a drag-free satellite, which can potentially be used for navigation, geodesy and fundamental science experiments as well as ground based applications.