Jeffrey Zhu and Michael J. Coleman, U.S. Naval Research Laboratory

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For years, The Naval Research Laboratory (NRL) Advanced PNT branch has been operating an ensemble timescale to achieve a realization of UTC. Recently, NRL developed a second timescale using a separate measurement system. Having a second timescale increases the resilience of NRL’s UTC realization. Each timescale can be used to cover gaps or correct anomalies in the other. A second timescale will allow NRL to provide a continuous UTC realization even if one timescale has to be interrupted for maintenance or transportation. To make the second timescale a viable alternative, NRL uses a LQC Gaussian steering algorithm to steer the two timescales together. This paper describes the formation of a timescale from an ensemble of atomic clocks. Two timescales derived from different measurement systems are presented and compared to demonstrate the steering algorithm and general ensemble stability.