Design of a compact virtual retroreflector for future satellite gravimetry missions

Abstract

This thesis presents the design, modeling, and experimental characterization of a compact virtual retroreflector intended for next-generation satellite gravimetry missions. Inspired by the success of missions like GRACE and GRACE-FO - which demonstrated the effectiveness of laser interferometry in precisely measuring Earth’s gravity field, future missions are shifting toward constellations of small satellites to enhance temporal resolution and reduce costs. This evolution demands miniaturized, stable optical components suitable for CubeSat platforms. Expanding on the Triple Mirror Assembly (TMA) concept used in GRACE-FO, this work investigates the optical and partial mechanical behavior of a 3D-printed retroreflector. The prototype was evaluated using heterodyne interferometry to measure phase changes, with particular focus on polarization response, power stability, and tilt-to-length (TTL) coupling. CAD-based dynamic simulations estimated structural resonance frequencies, while experimental measurements assessed beam coalignment accuracy and the system’s sensitivity to tilt-induced pathlength variations and polarization changes. This prototype serves as an initial proof of concept, providing valuable data to guide further development. The study established a robust measurement setup and conducted a preliminary feasibility analysis of a compact retroreflector design. These findings lay a solid foundation for future work, supporting the ongoing development of miniaturized optical systems for space-based gravimetric sensing and highlighting key design considerations for small satellite applications.