{'fraction_non_alphanumeric': 0.025217391304347827, 'fraction_numerical': 0.011304347826086957, 'mean_word_length': 4.454976303317536, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Frequency steering of hydrogen masers

The two Master Clock (MC) systems at USNO are steered in frequency so as to equalize their times with that of a mean timescale produced by an ensemble of hydrogen masers and cesium standards weighted dynamically and revised by post-processing. Occasional steers are also made to keep UTC (USNO) close to TAI. Experiments have been made with different steering algorithms in a search for an optimal one, i.e. that equalizes the times of an MC and the mean timescale satisfactorily closely and quickly without destabilizing the MC's maser to an extent noticeable by our users. Such a choice appears to be one wherein 10 or 90 days of data are averaged to determine the MC's frequency, a damping factor (time constant) of 100 days is employed in the time equalization, and an upper limit of 3.5 parts in 10/sup 15/ is set on the maximum daily frequency change. An algorithm utilizing linear quadratic Gaussian control of Kalman-filtered data is being tested on one MC. The absolute frequency stability of UTC (USNO) appears to be comparable to that of TAI. A back-up USNO MC has been established at Falcon AFB, CO.