ISSN:0048-6604    

DOI:10.1029/RS014i004p00519

年代:1979

数据来源: WILEY

摘要:

The roles which spectral density of fractional frequency fluctuations, two‐sample variance, and power spectra play in different parts of the electromagnetic spectrum are introduced. Their relationship is discussed. Data acquisition in the frequency and the time domain is considered, and examples are given throughout the spectrum. Recently proposed methods for the characterization of a single high‐quality frequency source are briefly described. Possible difficulties and limitations in the interpretation of measurement results are specified, mostly in the presence of a dead time between measurements. The link between past developments in the field, such as two‐sample variance and spectral analysis from time domain measurement, and recently introduced structure functions is empha

ISSN:0048-6604    

DOI:10.1029/RS014i004p00521

年代:1979

数据来源: WILEY

摘要:

The helium‐neon methane‐stabilized laser frequency at 88 THz (3.39 μm) and higher frequencies (148 and 197 THz, frequencies of the Xe (2.03 μm) and Ne (1.52 μm) lasers) have been measured by comparison with the cesium frequency standard using a microwave to visible frequency synthesis chain. This paper will report on the techniques of laser frequency measurements, the nonlinear devices used for these measurements, and the different methods for laser frequency synthesis with emphasis on microwave and laser generators. The extension of laser frequency measurements to the visible will also be dis

ISSN:0048-6604    

DOI:10.1029/RS014i004p00541

年代:1979

数据来源: WILEY

摘要:

Today's time and frequency standards which are in active use ranging from the definition of the second to spacecraft applications are all based on atomic resonances in the microwave region controlling high‐performance quartz crystal oscillators. The present status of these standards will be presented focusing in particular on cesium, hydrogen, and rubidium devices, as well as on new quartz crystal standards. A coherent picture of their physical principles and limitations is given based on the common attempt to reduce perturbations and Doppler effects. The sharpness of the resonance line is linked to the flicker noise stability limit of the various standards, and some speculation is made on where and how much further improvements may occur. It is demonstrated how new design concepts and new physical methods most likely will significantly improve the accuracy, stability, and practical usefulness of time and frequency standard

ISSN:0048-6604    

DOI:10.1029/RS014i004p00561

年代:1979

数据来源: WILEY

摘要:

The properties of stable lasers are discussed. Consideration is given to the methods of production of lasers with a very narrow linewidth of about 0.5 Hz and to their use in achieving high values of long‐term frequency stability and reproducibility. The results of investigations of frequency stability of a He‐Ne laser with a methane absorbant and a telescopic beam expander are presen

ISSN:0048-6604    

DOI:10.1029/RS014i004p00573

年代:1979

数据来源: WILEY

摘要:

A review is made of developments in wavelength measurement practice over the last 5 years. The rapid development of single‐frequency tunable dye lasers has led to a requirement for quick and easy wavelength measurement at accuracies of 1 part in 106or better. This has stimulated the development of moving‐carriage interferometers and of methods of image sensing with detector arrays or vidicon tubes. There has also been progress in the attainment of very high accuracy in wavelength comparisons of stabilized lasers, now nearly matching the laser reproducibilities of a few parts in 1011. The limitations to accuracy seem to be predominantly the defects of optical surfaces and uncertainties arising from diffraction effe

ISSN:0048-6604    

DOI:10.1029/RS014i004p00585

年代:1979

数据来源: WILEY

摘要:

First the concepts of time and of time scales are discussed. Then the paper deals with the definition of time scales and with the relevant resolutions and recommendations of international organizations. After a discussion of frequency and time standards, at present of importance with respect to time scale production, clock models describing the clock behavior are treated. This is followed by a review of problems of time comparisons and a description of time service equipment and methods. Then averaging and extrapolation problems are discussed. The present qualities of the international atomic time and of atomic time scales produced by time‐keeping institutes are finally reviewe

ISSN:0048-6604    

DOI:10.1029/RS014i004p00593

年代:1979

数据来源: WILEY

摘要:

A brief review of the research accomplishments by NASA in meeting the needs of the space program for precise time in satellite tracking is presented. As a major user of precise time signals for clock synchronization of NASA's worldwide satellite tracking networks, the agency provided much of the necessary impetus for the development of stable frequency sources and time synchronization technology. The precision in time required for both satellite tracking and space science experiments has increased at a rate of about 1 order of magnitude per decade from 1 ms in the 1950's to 100 μs during the Apollo era in the 1960's to 10 μs in the 1970's. In the 1980's, when the Tracking and Data Relay Satellite System (TDRSS) comes into operation, satellite timing requirements will be extended to 1 μs and below. These requirements are needed for spacecraft autonomy and data packeting which are now in active planning stag

ISSN:0048-6604    

DOI:10.1029/RS014i004p00605

年代:1979

数据来源: WILEY

摘要:

The current view of space‐time chronometry is reviewed in its different elements, clock transport and the ‘twin paradox,’ the effect of a gravitational field, and the Doppler effect. In this view a class of privileged, local inertial frames is assumed, and all good clocks measure proper time, the only observable one needs. Relativistic effects on clock synchronization and frequency comparison are described, and the essential role of the geoid is stressed. The available experimental precision makes these effects an essential ingredient of current and future work in this field. The role of distant matter in determining inertia and local dynamics (‘Mach's principle’) is not adequately described in this view. The cosmic background radiation provides a precise definition and a measurement of the local standard of rest with respect to the universe, which might have a privileged character among all the inertial frames. Different kinds of violations of the conventional view based upon this conjecture are discussed in terms of free dimensionless parameters. Finally, we review the upper bounds to the discrepancies from the relativistic values as deduced from several ex

ISSN:0048-6604    

DOI:10.1029/RS014i004p00621

年代:1979

数据来源: WILEY

摘要:

The atomic clock is the nearest approximation we have to the hypothetical proper clock of the ‘gedanken,’ or thought, experiments that are used to illustrate the new relativistic or gravitational phenomena identified in post‐Newtonian studies of gravitation. The recent decades of progress in space technology have made the whole solar system accessible as a laboratory for gravitation, and the atomic clock with stability in the 10−16domain offers a method of measuring distance and velocity as well as being an experimental device to probe the behavior of time. Experimental gravitation, which is now nearly synonymous to experimental relativity, is reviewed in the context of modern experimental techniques, and the role of the clock is discussed in detail. A catalog of experiments, based on four classes of experiments as described by Misner et al. (1970), is used to identify the particular aspect of gravity that is being tested, and the application of the clock is discussed in ea

ISSN:0048-6604    

DOI:10.1029/RS014i004p00629

年代:1979

数据来源: WILEY