Interferometric Range Transceiver for Measuring Temporal Gravity Variations

We report on interferometric range transceiver technology demonstration. The goal of this work is to reduce risk for a follow-on gravity mission to the Gravity Recovery and Climate Experiment (GRACE) by demonstrating performance of a heterodyne interferometric laser ranging instrument appropriate for a follow-on gravity mission to GRACE at the NASA Technology Readiness Level (TRL) 6. In order to show readiness at TRL 6 we are constructing a brassboard interferometer from flight qualifiable material that we will run through vibration and thermal tests. We have demonstrated displacement noise performance of better than 1 nm/√Hz at frequencies greater than 30 mHz in a laboratory breadboard.