Composite USO/CSAC timekeeping system

The recent introduction of a first generation of chip scale atomic clocks (CSAC) offers an opportunity to enhance space-based communication and navigation systems with their unique aspects of frequency accuracy and very low size, weight and power. Nonetheless, CSAC frequency noise levels are likely too high to be used directly as master frequency sources in deep space communication systems. Composite clock systems combine complementary frequency sources to utilize the best accuracy and stability of each source to extend the overall performance of the clock system. We will discuss our research work toward a composite ultra-stable oscillator (USO)/CSAC timekeeping system. Such a system would preserve the low noise and excellent short term stability of the quartz USO while using the CSAC technology as an augmentation for clock drift correction and monitoring for in-situ frequency disturbance during autonomous operation.