Comment on: Holographic interferometry applied to measurements of small static displacements of diffusely reflecting surfaces.
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Vest, C. M.↗
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Results for “INTERFEROMETRY”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Precision selenodesy via differential interferometry.
Review of the first results obtained from the development and use of a new type of differential receiver designed to determine the relative locations on the lunar surface of two Apollo-deposited transmitters. This receiver has made it possible to reduce random and systematic instrumental errors to nearly negligible levels (displacement uncertainties equivalent to a few centimeters).
Counselman, C. C., III↗
Two frequency radar interferometry applied to the measurement of ocean wave height.
Description of a technique for measuring the rms wave height averaged over an area of the sea that is much greater than any horizontal scale of the surface waves. The measurement method involves a nadir looking radar that transmits and receives two continuous monochromatic signals simultaneously. Signal processing at the receiver requires the computation of a correlation function which is shown to depend only on the statistical rms surface elevation of specular points and not on the temporal or spatial frequency spectrum of the wave height or slope. Laboratory measurements have been conducted on wind driven waves, and the measured correlation function compares favorably with the underlying theory.
Weissman, D. E.↗
Very-long-baseline interferometry techniques applied to problems of geodesy, geophysics, planetary science, astronomy, and general relativity.
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Counselman, C. C., III↗
Combined effects of a converging beam of light and mirror misalignment in Michelson interferometry
Expressions have been derived and calculations have been made which show that combined effects lead to asymmetric interferograms and reduction in power at zero path difference. Criteria are given for estimating maximum allowable mirror misalignment.
Kunz, L. W.↗
Optical Signal Processing: Poisson Image Restoration and Shearing Interferometry
Optical signal processing can be performed in either digital or analog systems. Digital computers and coherent optical systems are discussed as they are used in optical signal processing. Topics include: image restoration; phase-object visualization; image contrast reversal; optical computation; image multiplexing; and fabrication of spatial filters. Digital optical data processing deals with restoration of images degraded by signal-dependent noise. When the input data of an image restoration system are the numbers of photoelectrons received from various areas of a photosensitive surface, the data are Poisson distributed with mean values proportional to the illuminance of the incoherently radiating object and background light. Optical signal processing using coherent optical systems is also discussed. Following a brief review of the pertinent details of Ronchi's diffraction grating interferometer, moire effect, carrier-frequency photography, and achromatic holography, two new shearing interferometers based on them are presented. Both interferometers can produce variable shear.
Hong, Yie-Ming↗
Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing
The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.
Kong, J. A.↗
Thermal stress studies using optical holographic interferometry
The application of holography to thermal stress studies is discussed. Interference fringes as produced by holograms and their interpretation are reviewed in relation to workpiece displacement. Three potential mechanisms are given to explain thermal displacement as detected by holographic methods. Results of some thermal stressing studies are reported, including tests on a live rocket motor.
Harris, W. J.↗
Combined effects of a converging beam of light and mirror misalignment in Michelson interferometry
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Kunz, L. W.↗
Investigation of acoustic radiation from supersonic turbulent jets by double-pulse holographic interferometry
A new experimental method was used to optically investigate the acoustic field radiated from supersonic jets. The method utilizes a pulse ruby laser to obtain double exposure holograms of the sound field of a supersonic jet. The jet remains on during both exposures thus eliminating the no-flow exposure. The time separation between the pulses can be varied depending on the spectral component of the radiation to be observed. Optical records were obtained for supersonic jets with exit Mach number 1.0, 1.5 and 2.0. It was found that high frequency acoustic radiation mainly originates from the regions near the nozzle exit, whereas the low frequency noise is generated from regions further downstream. These findings are consistent with the acoustic data obtained by other investigators.
Ozkul, A.↗
High resolution interferometry of the sun at 3.7 cm wavelength
The results of interferometric solar observations at a wavelength of 3.7 cm with effective resolutions of 7 and 15 sec are discussed. Observations have shown that a small-scale quasi-periodic component was present in solar radio emission from the entire solar disk and that this component contained a circularly polarized fraction of less than 10%. The theory of gyroradiation and gyro-resonant absorption is applied in the interpretation of the S-component of solar radio emission.
Lang, K. R.↗
Long base line interferometry of the sun at centimeter wavelengths
The three-element interferometer of the National Radio Astronomy observatory and the two-element interferometer of the Hat Creek Observatory have been used to observe the fine structure of the sun at 11.1-, 3.7-, and 1.3-cm wavelengths. Solar active regions have been synthesized at 11.1- and 3.7-cm wavelengths with angular resolutions of 9 and 3 arc sec, respectively. Structural components on the scale of a few seconds of arc have also been detected in the quiet-sun and flare regions.
Kundu, M. R.↗
High angular resolution and position determinations by infrared interferometry
Interferometer systems are described in the form of publications and reports. 'Distance Meter Helps Track the Stars', 'Berkeley Heterodyne Interferometer', 'Infrared Heterodyne Spectroscopy of CO2 on Mars', and 'A 10 micron Heterodyne Stellar Interferometer' are papers reported.
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Time, geodesy, and astrometry: Results from radio interferometry
The results from a total of a dozen transcontinental and intercontinental VLBI experiments are discussed. Particular emphasis is placed on: (1) the inferred behavior of the frequency standards, usually hydrogen masers, on time scales from 10 to 100,000 seconds; (2) the estimated celestial positions of the observed radio sources; (3) the determinations of the vector baselines; and (4) the inferred values of polar motion and UT.1.
Clark, T. A.↗
Microwave interferometry technique for obtaining gas interface velocity measurements in an expansion tube facility
A microwave interferometer technique to determine the front interface velocity of a high enthalpy gas flow, is described. The system is designed to excite a standing wave in an expansion tube, and to measure the shift in this standing wave as it is moved by the test gas front. Data, in the form of a varying sinusoidal signal, is recorded on a high-speed drum camera-oscilloscope combination. Measurements of average and incremental velocities in excess of 6,000 meters per second were made.
Laney, C. C., Jr.↗
Microwave interferometry of Saturn: Application to the brightness temperature of the rings
Radio interferometric measurements of Saturn and Saturn's rings are explained. The measurements are limited to Mu is greater than or equal to 3. Data are also given on visibility functions, flux density, and brightness temperature.
Berge, G. L.↗
An investigation of traction in elastohydrodynamic point contacts using optical interferometry
An optical EHD machine is described which will measure the thickness of elastohydrodynamic lubricant films in rolling/sliding contacts while a traction force is applied to the film. A convenient way of plotting friction coefficient against slide/roll ratio is proposed. For 13 pure fluids with well-established physical properties, the value of the peak friction coefficient was found to lie between 0.011 and 0.09.
Gentle, C. R.↗
Solar gravitational deflection of radio waves measured by very-long-baseline interferometry
Utilizing a four-antenna technique, simultaneous observations were made, at each end of an 845-km baseline, of the radio sources 3C279 and 3C273B, which are 10 deg apart in the sky. Differences in interferometric phases at 3.7-cm wavelength monitored near the time of the 1972 occultation of 3C279 by the sun, yielded a gravitational deflection of 0.99 plus or minus 0.03 times the value predicted by general relativity, corresponding to gamma = 0.98 plus or minus 0.06 (standard error).
Counselman, C. C., III↗