New PDF release: An Assessment of Precision Time and Time Interval Science

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

ISBN-10: 0309085225

ISBN-13: 9780309085229

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

Knowledge of time is key to express wisdom of situation, and accordingly the army, with its have to navigate at the excessive seas, has traditionally performed an enormous position within the improvement and alertness of complicated time recognition and dissemination applied sciences. Discoveries coming from simple study funded by way of the workplace of Naval examine (ONR) lie on the middle of ultra-modern maximum functionality atomic clocks, Naval learn Laboratory (NRL) services performed a task in constructing the space-qualified atomic clocks that let the worldwide Positioning approach (GPS), and the U.S. Naval Observatory (USNO) keeps and disseminates the traditional of time for the entire division of safeguard (DOD). The military has made significant investments in so much facets of precision time and time period (PTTI) technology and expertise, even supposing particular PTTI-related examine has additionally been funded via the safety complex learn tasks enterprise (DARPA) and non-DOD corporations akin to the nationwide technological know-how beginning (NSF), the nationwide Aeronautics and house management (NASA), and the dep. of trade. military investment, mostly via ONR, has a heritage of being an early enabler of key new advancements. sensible investment judgements by way of the Navy-particularly by way of ONR application officers-have underpinned many of the significant advances in PTTI technological know-how and know-how (S&T) within the final 50 years.

PTTI is critical to trendy naval wishes, and certainly to all of the armed prone, to be used in either navigation and communications. distinct 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. distinctive frequency keep watch over is needed in communications for spectrum usage and frequency-hopped spread-spectrum strategies. there are lots of examples of crucial army operations that rely on PTTI and will reap the benefits of advancements in PTTI know-how. those comprise:

-GPS clocks and self reliant operations,

-Weapon method 4-dimensional coordination,

-GPS antijamming,

-Network-centric war, and

-Secure army communications.

This document summarizes that discounts within the measurement, weight, and gear standards and raises within the ruggedness of PTTI units with no sacrificing functionality could positioned extra exact and distinctive timekeeping within the fingers of the warrior, enhancing features in all the above operations.

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Additional resources for An Assessment of Precision Time and Time Interval Science and Technology

Example text

S. university work in atomic physics gets presented at physics conferences rather than at the IEEE-IFCS. S. university contributions in acoustics is largely attributable to sensor papers. S. contributions and those of other countries at the IEEE-IFCS conference. S. contributions is dramatic, and the 1999 conference—which was held in Europe in conjunction with the European Frequency and Time Forum—indicates the magnitude of foreign contributions. The United States lags behind France, Japan, and other countries in supporting university research in PTTI applications.

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. One such source is temperature fluctuations, which cause frequency changes dependent on the temperature coefficients of the resonator and other sensitive elements.

They can also cause changes in the heat transfer, thus indirectly inducing frequency changes due to temperature variations. A welldesigned quartz LO will change less than ±5 × 10–9 with a pressure change of 1 atmosphere. Atomic resonators can also be affected by atmospheric pressure changes, either through direct 21 STATE OF THE ART OF PTTI PHYSICS AND DEVICES interaction or through indirectly inducing temperature changes. In rubidium gas cell standards, the gas cell deformation is pressure dependent, inducing buffer gas density changes.

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An Assessment of Precision Time and Time Interval Science and Technology 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

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