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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Context sensitive formulations of antenna pattern correction and side lobe compensation for NOSS/LAMMR real time processing

Large antenna multi-channel microwave radiometer (LAMMR) software specifications were written for LAMMR ground processing. There is a need to determine more computationally-efficient antenna temperature correction methods in compensating side lobe contributions especially near continents, islands and weather fronts. One of the major conclusions was that the antenna pattern corrections (APC) processes did not accomplish the implied goals of compensating for the antenna side lobe influences on brightness temperature. A-priori knowledge of land/water locations was shown to be needed and had to be incorporated in a context sensitive APC process if the artifacts caused by land presence is to be avoided. The high temperatures in land regions can severely bias the lower ocean response.

Chin, R. T.↗
NASA NTRS1982

Cultural and environmental effects on the spectral development patterns of corn and soybeans: Field data analysis

An overall approach to crop spectral understanding is presented which serves to maintain a strong link between actual plant responses and characteristics and spectral observations from ground based and spaceborne sensors. A specific technique for evaluating field reflectance data, as a part of the overall approach, is also described. Results of the application of this technique to corn and soybeans reflectance data collected by and at Purdue/LARS indicate that a number of common cultural and environmental factors can significantly affect the temporal spectral development patterns of these crops in tasseled cap greenness (a transformed variable of LANDSAT MSS signals).

Crist, E. P.↗
NASA NTRS1982

Association of spectral development patterns with development stages of corn

Association is made between the development stages of corn as defined by Hanway and the temporal-spectral development pattern of corn in a transformed data space derived from Landsat-MSS band reflectance values, using field-collected reflectance and associated data. Results indicate that the spectral vegetation index used (a reflectance equivalent of Tasseled Cap Greenness) reaches a maximum well before the stage at which corn is expected to achieve its peak leaf area index. Possible physiological and canopy geometry related causes for this and other results are presented.

Crist, E. P.↗
NASA NTRS1981

Realizable feed-element patterns for multibeam reflector antenna analysis

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Rahmat-Samii, Y.↗
NASA NTRS1981

Ejecta patterns diagnostic of planetary rotations

A new scheme for determining a body's rotational history from the geological record is presented. Trajectories of ejecta on a rotating object are affected by the Coriolis effect in a manner characteristic of the direction and speed of the object's spin. This information is registered on the surface in the form of debris deposits and ray patterns, and can be interpreted by comparing photographs of the planet's surface with specified paradigms. This approach has the advantage of being independent of the body's internal structure and of relating its rotational history directly to its cratering chronology. This approach could be used, for example, to date the despinning of Mercury relative to its latest bombardment.

Dobrovolskis, A.↗
NASA NTRS1982

Synthesis of offset dual reflector antennas transforming a given feed illumination pattern into a specified aperture distribution

The problem of transforming a given primary feed pattern into a desired aperture field distribution through two reflections by an offset dual reflector system is investigated using the concepts of geometrical optics. A numerically rigorous solution for the reflector surfaces is developed which realizes an exact aperture phase distribution and an aperture amplitude distribution that is accurate to within an arbitrarily small numerical tolerance. However, this procedure does not always yield a smooth solution, i.e., the reflector surfaces thus realized may not be continuous or their slopes may vary too rapidly. In the event of nonexistence of a numerically rigorous smooth solution, an approximate solution that enforces the smoothness of the reflector surfaces can be obtained. In the approximate solution, only the requirement for the aperture amplitude distribution is relaxed, and the condition on the aperture phase distribution is continued to be satisfied exactly.

Mittra, R.↗
NASA NTRS1982

Rocket photographs of fine structure and wave patterns in the solar temperature minimum

A new series of high resolution pictures of the sun has been obtained during the second flight of the Transition Region Camera which occurred on September 23, 1980. The qualitative analysis of the results indicates that a substantial portion of the solar surface at the temperature minimum radiates in non-magnetic regions and from features below 1 arcsec in size. Wave patterns are observed on the 160 nm temperature minimum pictures. They are absent on the Lyman alpha pictures. Their physical characteristics are compatible with those of gravitational and acoustic waves generated by exploding granules.

Bonnet, R. M.↗
NASA NTRS1982

Far-field radiation patterns of Y and T shaped arrays with Chebyshev loading

The far-field radiation patterns for Chebyshev loaded Y- and T-shaped array antennas are given for a number of cases. Included are full- and half-length loaded array arms. The goal of the investigation is to determine the effect of different Chebyshev loading arrangements on this type of array. It is found that in both the Y- and T-shaped arrays, the main lobes are defined by the shape of the array and that the level of the side-lobes is mainly dependent on the Chebyshev loading (that is, complete or partial).

Gabriel, A. K.↗
NASA NTRS1983

Test Pattern for IC's

Random-fault densities measured in array of standard structures. Test pattern is array of standard circuit elements built into circuit chip along with, or in lieu of, integrated circuit objective process. Measurements on ray made and interpreted so fabrication process can be corrected as necessary.

Griswold, T. W.↗
NASA NTRS1982

Analysis of airborne antenna patterns

The status of various efforts in support of the development of computer codes to analyze the radiation patterns of general aviation aircraft and simulate private aircraft is reported. Because of the significant amount of energy scattered by the windshield of private aircraft, a method is being developed to treat high frequency scattering by thin dielectric layers. To treat such aircraft at lower frequencies, i.e., where the aircraft surface area is less than 10 square wavelengths, a moment method code is being modified. The problem of plane (or surface) wave diffraction by the dielectric half plane is constructed and discussed.

Rojas, R. G.↗
NASA NTRS1983

Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

Various flow visualization techniques were used to define the secondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious.

Gaugler, R. E.↗
NASA NTRS1983

Proceedings of the NASA/MPRIA Workshop: Pattern Recognition

Outlines of talks presented at the workshop conducted at Texas A & M University on February 3 and 4, 1983 are presented. Emphasis was given to the application of Mathematics to image processing and pattern recognition.

Guseman, L. F., Jr.↗
NASA NTRS1979

Full scale LANDSAT-D antenna pattern measurements

The design verification of the LANDSAT-D antenna subsystem is addressed. In particular, the analysis of the antenna radiation patterns utilizing a full scale mockup of the LANDSAT-D satellite is discussed. Test antennas included two S-Band shaped beam antennas, two S-Band omni unit radiators (to operate in array), a GPS antenna, an X-Band shaped beam antenna, and one S-Band high-gain parabolic antenna.

Source record↗
NASA NTRS1983

Patterns of fracture and tidal stresses on Europa

A comparison of dark band, triple band, and cuspate ridge orientations with the fracture patterns predicted for tidal distortion due to orbital recession and eccentricity is undertaken, to test the hypothesized identification of Europa's lineaments as tidal distortion and planetary volume change fractures. Short, reticule dark bands near the anti-Jove point could be tension cracks caused by orbital eccentricity. Long, arcuate dark bands and triple bands peripheral to the anti-Jove point may be strike-slip faults due to orbital recession. The orientation and distribution of cuspate ridges, if they are compressional, suggests their formation in response to a combination of orbital recession and planetary volume decrease. If surface fracturing is due to tidal deformation, important constraints are exerted by it on Europa's orbital evolution.

Helfenstein, P.↗
NASA NTRS1984

Secondary pattern computation of an arbitrarily shaped main reflector

The secondary pattern of a perfectly conducting offset main reflector being illuminated by a point feed at an arbitrary location was studied. The method of analysis is based upon the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO) and geometrical theory of diffraction (GTD). Key features of the reflector surface is completely arbitrary, the incident field from the feed is most general with arbitrary polarization and location, and the edge diffraction is calculated by either UAT or by UTD. Comparison of this technique for an offset parabolic reflector with the Jacobi-Bessel and Fourier-Bessel techniques shows good agreement. Near field, far field, and scan data of a large reflector are presented.

Lam, P. T. C.↗
NASA NTRS1984

Patterns of magnetic field merging sites on the magnetopause

Models of the magnetospheric and magnetosheath magnetic fields are used to determine the relative orientations of the two near the dayside magnetopause for the purpose of locating potential merging sites. Areas of the magnetopause with various degrees of antiparallelness for different Interplanetary fields as contour diagrams are studied. For southward and GSE-Y interplanetary field, the patterns obtained are consistent with those envisioned by Crooker in an earlier analysis which used simplified representations for the magnetic field geometry. Here the application of realistic models shows the locations of areas where any antiparallel component occurs. Merging sites for radial interplanetary fields are also illustrated. The results suggest that the geometrical configuration of the fields is suitable for merging over a large fraction of the magnetopause for interplanetary fields that are either primarily southward, GSE-Y, or radial (GSE-X) in direction.

Luhmann, J. G.↗