Development of a space-compatible packaging system for an integrated monolithic ultra-stable optical reference.

We report the development of a space-compatible packaging system for an integrated monolithic ultra-stable optical reference toward China's next-generation geodesy mission with low orbit satellite-to-satellite tracking. Building on our previous work, we optimized the mounting structure and thermal insulation mechanism using the finite element method. The comprehensive simulation results demonstrated the robustness of the entire packaging system with enough margins to withstand severe launch loads and maintain an ultra-high geometric cavity length stability. A long-term prediction of the vacuum maintenance around the cavity during in-orbit operation was conducted. An engineering prototype, within which an integrated monolithic optical reference has been mounted, was built based on our optimized design, and it has successfully passed typical aerospace environmental tests, including sinusoidal vibration (∼10 g, 10-100 Hz), random vibration (∼0.045 g2/Hz, 10-2000 Hz), and thermal cycling (0-45, 3 °C/min, lasting for 90 h). The experimental thermal time constant of the prototype exceeded 9.5 × 104 s, enabling a temperature stability of 1.1 × 10-6 K/Hz1/2 at 10 mHz on the optical cavity, with external active temperature control. The design is also suitable and useful for laboratory and terrestrial applications.