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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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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The Nimbus-4 backscatter ultraviolet (BUV) atmospheric ozone experiment two years operation

The Backscatter Ultraviolet (BUV) experiment aboard the Nimbus-4 satellite is discussed. This double monochromator experiment measures ultraviolet terrestrial radiance at 12 discrete wavelengths between 2550 A and 3400 A. Approximately 100 scans covering a 230 kilometer square are made between terminator crossings on the daylight side of the earth. A colinear photometer channel with the same field of view is used to derive the Lambert reflectivity of the lower boundary of the scattering atmosphere. The extraterrestrial solar irradiance is measured at the northern terminator. The instrument has currently produced almost three years of nearly continuous data which are being used to infer the high-level ozone distribution and total ozone on a global basis. The high-level ozone data have been verified by independent coincident rocket ozone soundings, and the total ozone values show good agreement with Dobson spectrophotometer determinations as well as those made with the Infrared Interferometer Spectrometer also on Nimbus-4.

Heath, D. F.↗
NASA NTRS1973

A noncoherent model for microwave emissions and backscattering from the sea surface

The two-scale (small irregularities superimposed upon large undulations) scattering theory proposed by Semyonov was extended and used to compute microwave apparent temperature and the backscattering cross section from ocean surfaces. The effect of the small irregularities upon the scattering characteristics of the large undulations is included by modifying the Fresnel reflection coefficients; whereas the effect of the large undulations upon those of the small irregularities is taken into account by averaging over the surface normals of the large undulations. The same set of surface parameters is employed for a given wind speed to predict both the scattering and the emission characteristics at both polarizations.

Wu, S. T.↗
NASA NTRS1973

Backscattering from a two-scale rough surface with application to radar sea return

A two-scale composite surface scattering theory was developed without using the noncoherent assumption. The surface is assumed electrically homogeneous and finitely conducting; the surface roughness may be nonuniform geometrically. The special forms of the terms for excluding the non-coherent assumption and the meanings of these terms are discussed. To gain insight into the mechanisms of backscattering, the results are compared with those obtained by previous theories. The comparison with NRL data shows satisfactory agreement for both horizontal and vertical polarization, especially for incident angles larger than 30 deg. For smaller incident angles, NASA/JSC data have been chosen for comparison and close agreement is again observed.

Chan, H. L.↗
NASA NTRS1973

Confocal backscatter laser velocimeter with on-axis sensitivity.

A confocal backscatter laser Doppler velocimeter (LDV) that measures two velocity components has been developed. This device requires only two incident beams polarized normally to one another. Moreover, the velocity components sensed are nearly orthogonal. The velocimeter employs a combined dual-scatter, local oscillator arrangement to obtain the bidirectional sensitivity. Two photodetectors are used, each sensing only one Doppler frequency proportional to one of the very nearly orthogonal velocity components. In addition, a single Bragg cell serves to frequency bias both velocity components in order to eliminate directional ambiguity. A differencing technique has also been incorporated to enhance the dual-scatter Doppler signal corresponding to the transverse velocity.

Orloff, K. L.↗