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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Communications and tracking - Light and IR will help carry high traffic

The space station currently under consideration by NASA must simultaneously track and communicate with the many vehicles and objects surrounding it in orbit. While the Space Shuttle has 23 antennas, more than 50 will be required by the space station. In addition to Shuttle-compatible equipment at P, L, C, S, and Ku bands, the station system will probably incorporate Ka, W, IR and optical frequency equipment for tracking and communications. A major design challenge is foreseen in the placement of separate antennas, lenses and reflectors over the station's external geometry in order to give both the overlapping fields of view required for spherical coverage and the radiation of unambiguous navigation guide beams and markers. Adaptive distributed element arrays are under consideration. Another approach to spherical coverage involves the use of omnidirectional antennas which both transmit and receive RF energy over a wide range of angles.

Dickinson, R. M.↗
NASA NTRS1984

Integrating IR detector imaging systems

An integrating IR detector array for imaging is provided in a hybrid circuit with InSb mesa diodes in a linear array, a single J-FET preamplifier for readout, and a silicon integrated circuit multiplexer. Thin film conductors in a fan out pattern deposited on an Al2O3 substrate connect the diodes to the multiplexer, and thick film conductors also connect the reset switch and preamplifier to the multiplexer. Two phase clock pulses are applied with a logic return signal to the multiplexer through triax comprised of three thin film conductors deposited between layers. A lens focuses a scanned image onto the diode array for horizontal read out while a scanning mirror provides vertical scan.

Bailey, G. C.↗
NASA NTRS1984

Requirements for a passive IR advanced moisture and temperature sounder

The design of a high spectral resolution, lambda/delta lambda being approximately 1200 IR, sounder capable of increasing the vertical resolution of atmospheric temperature profiles and achieving a rms accuracy of approximately 1.5 K is discussed. This sounder permits improved determination of meteorological parameters on cloudiness, surface temperature, and air-surface interactions. A set of channels from the high J lines in the R branch of the 4.3-micron CO2 band complemented by a larger set of window, humidity, and temperature channels in the 3.7-, 6.3-, 9-, and 15-micron regions is used. Design and simulation studies show that such a sounder is within the present state of the art.

Chahine, M. T.↗
NASA NTRS1983

Developments with multispectral thermal-IR and active microwave systems - TIMS, SIR-A, SIR-B, and radarsat

An update of current and future systems for spectral scanning of geological features in the thermal-IR, and active microwave bands is presented. The design characteristics of four individual systems are described, including the NASA Thermal Infrared Multispectral Scanner (TIMS); the Shuttle Imaging Radars A and B (SIRA-A and SIRA-B); and the Canadian RADARSAT satellite for geological mapping and ice monitoring. The applications of spectral data from the Side Looking Airborne Radar (SLAR), the GEMS 100 mapping system, and the Landsat RBV instrument to the mapping of large geological structures are also described.

Harrison, P. G.↗
NASA NTRS1985

Physics and design of advanced IR bolometers and photoconductors

The state-of-the-art in photoconductors and bolometers is reviewed, centering on the materials development and concepts of extrinsic Si and Ge devices. It is suggested that in the field of 2-D detector arrays the hybrid circuits containing a photoconductor or a photodiode array, bonded with In solder to a switched MOS readout device with up to 60 x 60 elements, will produce superior performance. Other systems discussed include charge-coupled devices, developed for visible-light imaging and adapted to IR imaging, and charge-injection devices, a monolithic combination of a standard photoconductor and a metal-insulator-semiconductor capacitor. Finally, it is pointed out that a nonequilibrium theory of bolometer noise demonstrates the possibility of reducing the traditionally accepted noise limits by 60 percent for Johnson noise and 30 percent for the noise from phonons in the thermal link of the bolometer.

Haller, E. E.↗
NASA NTRS1983

Broadband transmission functions for atmospheric IR flux computations and climate studies

In order to reduce the size of precomputed tables which are used in the emissivity approach to computing IR radiation in a climate model, the three-dimensional transmission function in the water vapor bands is defined in this study by a simple regression equation consisting of three two-dimensional parameters. The transmittances in the 9.6 and 15 micron bands are individually parameterized as functions of the amount of scaled absorber. This approach can thus be applied to atmospheres with a variable CO2 concentration.

Chou, M.-D.↗
NASA NTRS1985

A cool anomaly off northern California - An investigation using IR imagery and in situ data

The OPTOMA (Ocean Prediction Through Observation, Modeling and Analysis) program is developing an ocean descriptive-predictive system for four-dimensional data assimilation. It is presently concerned with the mesoscale variability in the California Current System (CCS). The present paper has the objective to assess the relationship of surface temperature structure to subsurface temperature structure and flow fields. Surface temperature anomalies are related to the mesoscale horizontal advective and subsurface mass fields. The cool anomaly off northern California in summer 1982 is discussed, taking into account the temperature structure along transects, T-S variations and inferred water masses, variation of horizontal temperature patterns with depth, and synoptic information from IR data.

Rienecker, M. M.↗
NASA NTRS1985

The internal reference source (IRS) for diffuse infrared background experiment (DIRBE)

A means is described for providing internal calibration for the detectors for DIRBE, which is the Diffuse Infrared Background Experiment (a part of the Cosmic Background Explorer). The internal reference source (IRS) that is used consists of four thermal graybody sources coupled to an integrating sphere. The relative insensitivity of the DIRBE bolometers and the linear temperature dependence of the Rayleigh-Jeans law made bolometer stimulation over five orders of magnitude difficult, so four different sources were used with emitting areas varying by a factor of 10 to the 8th. A low heat capacity design with the necessary stability appears to be thin nichrome films on a sapphire substrate. Voltage stability to 0.01 percent is required for those near infrared bands that required stimulation on the Wien portion of the blackbody curve.

Silverglate, P.↗
NASA NTRS1986

Directional reflectance response in AVHRR red and near-IR bands for three cover types and varying atmospheric conditions

Surface directional red and near-infrared reflectances of bare soil, orchard grass, and fescue were extracted from a multitemporal data set to correspond to NOAA-7 Advanced Very High Resolution Radiometer (AVHRR) scanning and illumination geometry at 30 deg latitude. Radiances were simulated at satellite altitude and a ratio vegetation index was calculated. The results show that off-nadir directional reflectance measured at the surface in the red and near-IR portions of the spectrum are approximately maintained with AVHRR viewing and illumination characteristics. The two-channel reflectance response is such that the ratio vegetation index is more constant with scan angle and atmospheric conditions than individual channels. It is shown that inclusion of atmospheric and surface reflectance data can greatly improve interpretation of AVHRR data, when knowledge of the range of atmospheric conditions and approximate directional reflectances of major cover types are known.

Holben, B.↗
NASA NTRS1987

Compositional information for the Moon: Some characteristics of current near-IR spectra (telescopic and laboratory)

For the last decade telescopic near infrared spectra have been obtained for small lunar areas. Such spectra, with the ground truth foundation from lunar samples, have been used extensively to address a multitude of problems in lunar science. Much of the near infrared spectral reflectance data from both laboratory and telescopic measurements have recently been compiled in comparable formats and an initial comparative assessment of the available data using selected spectral parameters has been made. The objective is to develop a framework for the systematics of lunar near-IR spectra in order to better interpret spectra of unknown materials in terms of useful compositional information. Each spectrum was first classified according to its general character then a variety of parameters sensitive to mineralogy and alteration products were measured for each spectrum: band width, band strength, absorption band center near 1 micron, band symmetry, continuum slope, etc. The telescopic and laboratory data sets are briefly described. The comparative analysis shows that a few well known lunar spectral properties are evident in both sets, such as the systematic variation in pyroxene composition between the highlands and the mare. However, an additional gabbroic component can be detected in many highland craters.

Pieters, Carle M.↗
NASA NTRS1987

Optical and IR luminosity functions of IRAS galaxies

The optical and infrared luminosity functions are determined for a 60 micron flux-limited sample of 68 IRAS galaxies covering a total area of 150 deg sq. The IR function is in good agreement with that obtained by other authors. The shape of the optical luminosity function is similar to that of optically selected galaxy samples. The integrated light of most objects in the sample have (NII) to H alpha line flux ratios characteristic of HII-region galaxies. In the absolute magnitude range M sub J = -18, -22 about 14% of late-type galaxies are IRAS galaxies. The apparent companionship frequency is about twice as large as that for a comparable sample of non-IRAS late-type galaxies.

Vader, J. Patricia↗
NASA NTRS1986

Radiation fluctuation statistics in satellites and GCM's Cross correlations of albedo and IR with temperature, moisture, and dynamics

Cross-correlations were calculated between the radiation emitted and reflected from the top of the atmosphere and the temperature, horizontal wind and precipitable water in the middle troposphere. The study was extended to the time domain by filtering data for 1-2 and 2.5-6 day periods. The effects of cloud radiation were quantified by comparisons of IR full-sky and clear-sky values. Significant correlations were obtained between the middle atmospheric physical and dynamical parameters and the top of the atmosphere radiation.

Charlock, T. P.↗
NASA NTRS1986

High-temperature oxidation of a rapidly solidified amorphous Ta-Ir alloy

The oxidation products formed at 500 and 700 C on an amorphous Ta-44.5 at. pct Ir alloy in an Ar-0.1 percent O2 gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3-4 nm) layer of Ta2O5 formed at the surface of the alloy. Continued growth of the Ta2O5, which occurred very rapidly, involved diffusion of oxygen anions from the Ta2O5/gas interface to the alloy/Ta2O5 interface, where tantalum was selectively oxidized. Because the oxide grew more quickly than iridium could diffuse back into the alloy, the iridium coalesced into platelets of crystalline iridium-rich alloy that were oriented approximately parallel to the oxide/alloy interface, and which became embedded in a matrix of Ta2O5. The unoxidized core remained in the glassy state. The oxidation process and/or the dissolution of oxygen into the unoxidized alloy caused the alloy to become embrittled.

Cotell, Catherine M.↗
NASA NTRS1987

The discovery of an infrared reflection nebula surrounding R Coronae Australis IRS 5

The infrared source R CrA IRS 5 in the R CrA dark cloud has been mapped, and it is found that it is extended at H (1.6 micron) and at K (2.2 micron). The geometry of the data suggest that this object consists of a disk and polar reflection lobe surrounding a star, similar to GSS 30 in the Ophiuchus dark cloud and to SGS 1 in the NGC 1333 dark cloud. The illuminating star has an effective temperature below 8000 K, a luminosity less than 9 solar luminosities, and lies above the main sequence. The luminosity of this star is smaller than the luminosity of any other known star which illuminates an infrared reflection nebula.

Castelaz, Michael W.↗
NASA NTRS1987

Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources

High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.

Cohen, R. J.↗
NASA NTRS1987

The IR emission features - Emission from PAH molecules and amorphous carbon particles

Techniques for the assessment of the importance of the various forms of PAHs, and recent infrared observations concerning the PAH problem, are considered. Spectroscopic data suggest that the observed interstellar spectrum is due to both free molecule-sized PAHs producing the narrow features, and amorphous carbon particles contributing to the broad underlying components. Explanations for the multicomponent emission spectrum are discussed. A model of the emission mechanism for the example of chrysene is presented, and an exact treatment of the IR fluorescence from highly vibrationally excited large molecules shows that species containing 20-30 carbon atoms are responsible for the narrow features, although the spectra more closely resemble those of amorphous carbon particles. It is suggested that future emphasis should be placed on the spatial characteristics of the component spectra.

Allamandola, L. J.↗