ULTRASTABLE QUARTZ OSCTLLATOR FOR SPACECRAFT

Jerry R. Norton

Abstract: A new series of quartz oscillators that have excellent performance has been developed for use in spacecraft. Some oscillators using this design have demonstrated 24-hour aging rates of less than 1 x 10-11, 100-s Alian variances of 7x 10-, and a phase-noise floor of -158 dBc. Variations in resonator performance exceeding factors of 10 have been found during the evaluation of resonators using the same test oscillator; this finding indicates that oscillator performance is still dominated by the quartz resonator. SC cut resonators manufactured by different companies using a variety of mounting techniques and resonator enclosures have been used in this design. Some performance parameters are directly related to resonator type. The oscillators are designed to survive the rigorous environment of a rocket launch. They are projected to have a minimum useful life of 5 years in a space environment through the use of conservative design margins, high-reliability components, and a rugged mechanical package. A vibration isolation system is incorporated that attenuates the band of frequencies generated by currently available launch vehicles that could potentially damage the oscillator. The oscillators are compact and low weight and have low power consumption. A dual thermal insulating system using a unique Dewar Hask design and a space blanket (alternate layers of a porous spacer and radiation-reflective aluminized Mylar) is used to isolate critical oscillator components from the thermal environment and to reduce power consumption. The design of the Dewar flask, which is made from titanium, requires no pinch-off tubes or other protrusions outside of the basic cylindrical envelope of the Dewar. A clearly defined frequency versus ambient pressure change was recognized during development of these oscillators. Components used in the oscillator were identified as the main cause of the pressure sensitivity, but after these components were replaced, a pressure sensitivity remained that is related to individual resonators and resonator types.
Published in: Proceedings of the 21th Annual Precise Time and Time Interval Systems and Applications Meeting
November 28 - 30, 1989
Sheraton Hotel
Redondo Beach, California
Pages: 509 - 518
Cite this article: Norton, Jerry R., "ULTRASTABLE QUARTZ OSCTLLATOR FOR SPACECRAFT," Proceedings of the 21th Annual Precise Time and Time Interval Systems and Applications Meeting, Redondo Beach, California, November 1989, pp. 509-518.
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