Stabilized Reference Frequency Distribution for Radio Science with the Cassini Spacecraft and the Deep Space Network; Conference rept

摘要

A high-performance frequency distribution system which includes two key technologies, the Stabilized Fiber-optic Distribution Assembly (SFODA) and the Compensated Sapphire Oscillator (CSO), has been developed to provide state- of-the-art frequency reference in the NASA Deep Space Network (DSN). This frequency distribution system was developed to enable sensitive gravity wave searches and occultation experiments between earth-based antennas in the (DSN) and the Cassini spacecraft. The experiments, to be conducted at S, X, and Ka band, require the highest possible frequency stability over observation times from 1 second to 1 day. The DSN frequency and timing subsystem generates and distributes coherent signals to multiple antennas up to 30 km away. The SFODA measures and compensates for distribution-related phase perturbations, and the CSO provides short-term stability cleanup and low phase noise at the antenna. This paper provides an overview and update of the end-to-end performance frequency and timing subsystem. Focus is given to the final SFODA design and test results using a 16-km optical fiber under controlled test conditions. Test data show a factor of 1000 improvement in long-term stability when the active phase compensator is used, thus enabling degradation-free distribution from the highest performing atomic frequency standards. Recent measurements between two CSO standards are also presented.