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We report on a 32-MHz quartz temperature compensated crystal oscillator (TCXO) fully integrated with commercial CMOS electronics and vacuum packaged at wafer level using a low-temperature MEMS-after quartz process. The novel quartz resonator design provides for stress isolation from the CMOS substrate, thereby yielding classical AT-cut f/T profiles and low hysteresis which can be compensated to < ±0.2 parts per million over temperature using on-chip third-order compensation circuitry. The TCXO operates at low power of 2.5 mW and can be thinned to as part of the wafer-level eutectic encapsulation. Full integration with large state-of-the-art CMOS wafers is possible using carrier wafer techniques.

The recent introduction of a first generation of chip scale atomic clocks (CSAC) offers an opportunity to enhance space-based communication and navigation systems with their unique aspects of frequency accuracy and very low size, weight and power. Nonetheless, CSAC frequency noise levels are likely too high to be used directly as master frequency sources in deep space communication systems.Composite clock systems combine complementary frequency sources to utilize the best accuracy and stability of each source to extend the overall performance of the clock system. We will discuss our research work toward a composite ultra-stable oscillator (USO)/CSAC timekeeping system. Such a system would preserve the low noise and excellent short term stability of the quartz USO while using the CSAC technology as an augmentation for clock drift correction and monitoring for insitu frequency disturbance during autonomous operation.

The Time and Frequency Laboratory (TFL) at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) provides support to multiple NASA/JPL missions that span our solar system from the study of the Sun's coronal mass ejections (STEREO) to the examination of the outer planets and the Kuiper Belt objects (New Horizons). This support includes providing precise time and frequency to the integration and testing of flight hardware, frequency reference for spacecraft ranging and communications via the APL communications facility, and the time-stamping of ground receipt telemetry packets from various spacecraft. The TFL's ensemble of three high-performance cesium standards and three hydrogen masers are integrated to form the APL timescale that is the basis for estimating UTC-UTC (APL) and for evaluating the performance of the individual clocks. Traceability to the USNO, NIST, and UTC is maintained via GPS common-view and all-in-view time transfer. The TFL's clocks are also incorporated into the formulation of International Atomic Time (TAI). Recently, the TFL Master Clock was transitioned from a cesium-beam frequency standard to a hydrogen maser, and the frequency adjustments of UTC (APL) are now performed with a high-resolution offset generator. These changes have greatly improved the stability of UTC (APL) and have also improved our ability to steer to UTC.

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