Rubidium-Fountain Characterization Using the USNO Clock Ensemble

We have carried out stability comparisons between our rubidium fountain, built as a prototype for a continuously operating clock, and the USNO Maser Mean timescale. Long, continuous runs of the prototype system allow us to demonstrate fractional frequency-stability comparisons to the Maser Mean that integrate as white frequency noise, with a stability of 5times10
<sup>-

16</sup>
at one day. We have measured the frequency sensitivity of the rubidium fountain to various experimental parameters in order to establish the regulation required to reach a long-term stability of order 1times10
^-16
.