For over four decades, the Applied Physics Laboratory of Johns Hopkins University (JHU/APL) has supplied the U.S. military and commercial space sectors with a quartz oscillator of unsurpassed performance and reliability. Referred to as having Ultra-Stable performance, this oscillator has been given the nomenclature of USO. The current USO, at 1.2 kilograms and 1.1 watts steady-state power consumption, features time- dependent drift (aging) of less than 1×10 -11 per day and fractional frequency variance approaching 1×10 -13 over the range of 1 to 100 seconds. Our paper will present performance data and describe the unique advantages afforded by the use of quartz oscillators in deep space, including in-flight data that demonstrates no degradation to long-term frequency by repeated radiation exposures. We will also present an outlook of technology projects planned for the next 5 years, including the use of Kalman filtering, direct digital synthesis, and alternative piezoelectric materials. We will present our viewpoint that further development in quartz resonators for space applications will only gain in importance as communication needs expand into interplanetary networks.
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