A Stabilized 100-Megahertz and 1-Gigahertz Reference Frequency Distribution for Cassini Radio Science

Abstract

The development of the stabilized fiber-optic distribution assembly (SFODA) is reported. The system was developed to enable gravitational wave searches and atmospheric occultation experiments between the Cassini spacecraft and the NASA Deep Space Network. These experiments are conducted at 32-GHz (Ka-band) frequencies and demand the highest possible short-term and long-term frequency stability at Deep Space Station 25, a remote antenna 16-km distant from the frequency reference source. This article presents the final design of the SFODA and test results transmitting a 1-GHz reference signal over a 16-km optical fiber under controlled test conditions. The SFODA utilizes active feedback with a temperature-compensating fiber-optic reel to compensate for thermally induced phase variations over the 16-km fiber cable. 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.