Session P1b: Environmental Sensitivity of Clocks and Timing Systems

Frequency Comb Optical Reference Stabilization in a Thermally Unstable Environment for Space Applications
Cyrus Bry, Matthew Kelley, Stephanie Leifer, Paul Steinvurzel, The Aerospace Corporation
Location: Seaview A/B
Date/Time: Tuesday, Jan. 28, 4:00 p.m.

The Aerospace Corporation is developing a fully autonomous dual fiber laser optical frequency comb (OFC) CubeSat payload with the goal of demonstrating OFC operation for future space-based optical clocks and for next generation optical time and frequency transfer. The OFCs are 1.5 µm-centered and operate with a 200 MHz repetition rate. Our effort involves engineering the comb package and electronics to survive the launch environment and conditions of low-Earth orbit (LEO). A significant challenge to the payload development comes from the extreme temperature sensitivity of the optical reference laser critical to frequency stabilization of the OFCs. The optical reference was initially tested in thermal vacuum over a range of 10 °C to 60 °C and exhibited wavelength (frequency) drifts of more than ±5 pm (±625 MHz), exceeding the control range of the OFCs. Subsequently, we showed experimentally that an existing simple method can provide both the long-term and short-term necessary stabilization of the optical reference. By using an RF oscillator-derived feedback control loop, which could be GPS-disciplined, the optical reference was held to ±65 fm (s = 14 fm), stabilizing the repetition frequency of the OFC to ±9 Hz (s = 3.8 Hz) over 20 °C to 50 °C. The temperature range used in the experiments was derived from Thermal Desktop simulations of the payload hosted in a 12U CubeSat and exceeds the thermal drift expected in a complete LEO orbit. Thus, the results of thermal testing indicate that this method for optical reference stabilization is sufficient to maintain lock of the OFCs in LEO without the added cost and complexity of an atomic reference. Approved for