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An Assessment of Precision Time and Time Interval Science by National Research Council, Division on Engineering and

By National Research Council, Division on Engineering and Physical Sciences, Naval Studies Board, Committee for an Assessment of Precision Time and Time Interval Science and Technology

Committee for an evaluate of Precision Time and Time period technological know-how and expertise, nationwide examine Council, department on Engineering and actual Sciences, Naval experiences Board

Knowledge of time is key to express wisdom of situation, and accordingly the military, with its have to navigate at the excessive seas, has traditionally performed a huge position within the improvement and alertness of complicated time consciousness and dissemination applied sciences. Discoveries coming from uncomplicated study funded through the place of work of Naval examine (ONR) lie on the middle of modern-day maximum functionality atomic clocks, Naval learn Laboratory (NRL) services performed a task in constructing the space-qualified atomic clocks that permit the worldwide Positioning approach (GPS), and the U.S. Naval Observatory (USNO) continues and disseminates the traditional of time for the entire division of protection (DOD). The military has made significant investments in so much points of precision time and time period (PTTI) technological know-how and know-how, even if particular PTTI-related study has additionally been funded by means of the safeguard complex study initiatives supplier (DARPA) and non-DOD companies corresponding to the nationwide technology beginning (NSF), the nationwide Aeronautics and area management (NASA), and the dep. of trade. army investment, mostly via ONR, has a historical past of being an early enabler of key new advancements. really appropriate investment judgements by way of the Navy-particularly via ONR application officers-have underpinned lots of the significant advances in PTTI technological know-how and expertise (S&T) within the final 50 years.

PTTI is critical to fashionable naval wishes, and certainly to all of the armed providers, to be used in either navigation and communications. targeted time synchronization is required to successfully ascertain the beginning of a code series in safe communications, to accomplish navigation, and to find the placement of sign emitters. specified frequency regulate is needed in communications for spectrum usage and frequency-hopped spread-spectrum ideas. there are various examples of crucial army operations that rely on PTTI and will reap the benefits of advancements in PTTI expertise. those comprise:

-GPS clocks and self sustaining operations,

-Weapon process 4-dimensional coordination,

-GPS antijamming,

-Network-centric conflict, and

-Secure army communications.

This file summarizes that mark downs within the measurement, weight, and gear standards and raises within the ruggedness of PTTI units with out sacrificing functionality could placed extra exact and distinctive timekeeping within the fingers of the warrior, enhancing services in all the above operations.

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Briefing to the committee on March 26, 2002. 26 AN ASSESSMENT OF PRECISION TIME AND TIME INTERVAL SCIENCE AND TECHNOLOGY the importance to the Navy and the entire DOD of supporting their development cannot be overestimated. There are numerous past and current examples of PTTI-related investigations producing capabilities of operational value to the military. 2 investment. This device produces frequency stabilities and accuracies rivaling oven-controlled crystal oscillators while requiring only a small fraction of the operating power, and it is finding use in applications as diverse as navigational buoys and GPS receivers.

CHEMISTRY Many key performance parameters of clocks and oscillators are directly impacted by processes related to chemistry. Below, some aspects of chemistry that can potentially lead to higher-performance atomic clocks and local oscillators are identified. Solid-State Chemistry Solid-state chemistry research could further the availability of high-perfection quartz. Evidence indicates that the stability of quartz devices is limited by quartz imperfections, such as dislocations and impurities. The feasibility of growing dislocation-free, ultrahigh-purity quartz has been demonstrated in the United Kingdom, but there is still no method for producing amounts sufficient to meet DOD needs.

Retrace Retrace is how well the standard or LO reproduces its frequency after a powerdown and cold restart. The best quartz LOs can retrace within a few parts in 1010. Retrace of the best commercial cesium standards is about ±1 × 10–13. Retrace of rubidium gas cell devices is about ±5 × 10–11. Retrace of hydrogen masers is about ±1 × 10–13. Noise Frequency noise in quartz LOs is due partially to thermal noise in the resonator and noise in the sustaining amplifier. In addition, there are low-frequency sources of noise.

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