Time and Frequency Activities at the JHU Applied Physics Laboratory

Mihran Miranian, Jeffrey F. Garstecki, and Gregory L. Weaver

Peer Reviewed

Abstract:	The Time and Frequency Laboratory (TFL) at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) provides support to multiple NASA/APL 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 satellite communications facility, and the time-stamping of groundreceipt 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 Precise Point Positioning (GPSPPP) time transfer. The TFL’s clocks are also incorporated into the formulation of International Atomic Time (TAI). The TFL Master Clock is a hydrogen maser and the frequency adjustments of UTC(APL) are performed with a high resolution offset generator. This combination of hydrogen maser and high resolution offset generator along with our UTC-UTC(APL) estimation algorithm has made it possible to maintain UTC(APL) within 10 nanoseconds of UTC 95% of the time. During the past year, the TFL began performing daily GPSPPP time transfer with the USNO. Preliminary results indicate that this method of time transfer will yield the precision required that could allow APL to use UTC(USNO) and possibly the USNO clocks as remote clocks in the APL Time Scale. These results will be presented.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	988 - 991
Cite this article:	Miranian, Mihran, Garstecki, Jeffrey F., Weaver, Gregory L., "Time and Frequency Activities at the JHU Applied Physics Laboratory," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 988-991. https://doi.org/10.33012/2017.15057
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