A Solid-state System for Measurement of Integrated Refractive Index
A Solid-state System for Measurement of Integrated Refractive Index

Author: Richard O. Gilmer

Publisher:

Published: 1967

Total Pages: 28

ISBN-13:

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A solid-state phase system is presented which is capable of indicating the variability of the integrated refractive index over line-of-sight propagation paths with extreme reliability. The system has a stability, which is independent of path length, of 1 pp 108 / 24 hr and 1 pp 109 / sec. Measurement precision is limited only by the resolution of the output phase meter and is 0.5% of full scale. Tabulated design criteria, component specifications, and illustrated circuit schematics are presented. Refractive index measurements with the phase system taken across a 1.6-km reservoir are compared to the average of conventional meteorological measurements of refractive index taken at the midway point and two terminal points for a 5-day period. The two measurements show a correlation estimate of 0.99 over the 5-day period.

Monthly Catalog of United States Government Publications
Monthly Catalog of United States Government Publications

Author: United States. Superintendent of Documents

Publisher:

Published: 1968

Total Pages:

ISBN-13:

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February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index

Development of a Microwave Modulated, Dual Optical Wavelength Geodetic Distance-measuring Instrument
Development of a Microwave Modulated, Dual Optical Wavelength Geodetic Distance-measuring Instrument

Author: J. C. Owens

Publisher:

Published: 1968

Total Pages: 118

ISBN-13:

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The accuracy of optical distance measurements on horizontal paths is limited at present to several parts per million by uncertainty in knowledge of the average air density along the path. This report describes the development and testing of a prototype instrument capable of significant;y greater accuracy, probably as high as 0.1 ppm. The instrument makes simultaneous measurements of transit time using two superimposed beams of light which have different optical wavelengths but which are modulated at a common microwave frequency. From the difference in transit times for the two colors, plus the absolute transit for either one, the average refractive index along the path and hence the true geodetic path length can be determined. Tests over a 5.3 -km patch have given a standard error of 0.3 ppm in corrected distance, and it is believed that even better results can be obtained. The system is described in detail, including modifications that would significantly increase its accuracy and range.