An advanced synthesized ultra-stable oscillator for spacecraft applications

Current ultra-stable oscillator (USO) technology relies on highly precise quartz resonators that are selected based on the desired output frequency and stability. These constraints on the crystal specifications significantly increase the lead time and expense of each USO. Recent research and development efforts in USOs by The Johns Hopkins University Applied Physics Laboratory (JHU/APL) have focused on a frequency synthesized USO based on a standardized, fixed-frequency resonator. The result of these efforts is a synthesized USO that will provide a frequency reference for transponders and other on-board users on future space missions. The frequency reference is stable enough for radio-science and navigation applications (Allan deviation <1.5 /spl times/ 10/sup -13/ at /spl tau/ = 10 s), and is electronically adjustable to cover the entire deep-space communications band. This frequency agility allows in flight re-assignment of the transponder frequencies. The synthesized USO offers low mass and DC power consumption yet maintains world-class noise performance and frequency stability performance.