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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

An optical filtering system for remote sensing of phytoplankton and suspended sediment

Aerial photography revealing blue-green Anacystis phytoplankton blooms in the Potomac River is presented. Data scanned were near-IR, green, and yellow nadir radiance; concurrent ground measurements are correlated with these data, including salinity, Secchi disk depth, chlorophyll a concentration, and river depth. In nonbloomed areas, R (radiance) is proportional to the reciprocal of Secchi depth for the green and yellow filters; in bloomed areas, R is constant for the green filter and random for the near-IR and yellow filters.

Bressette, W. E.↗
NASA NTRS1977

Development of a spectral break in the nonthermal emission of AO 0235+164

Results are reported for braod-band photometry of the BL Lac object AO 0235+164 carried out over the spectral range from 0.36 to 3.5 microns in December 1975 and in October and November 1976. It is found that the continuum of this object steepened at visible wavelengths between December 1975 and October 1976, but maintained a relatively constant slope in the near-IR despite a factor-of-ten decrease in flux from the maximum level. Visible-wavelength data are cited which appear to suggest that the steepening of the visible spectrum occurred in less than 300 days, while the near-IR level may have been nearly constant. It is shown that the observed change in the spectral shape of the visible-wavelength continuum cannot be explained in terms of a 'composite' model consisting of an unchanging galaxy and a varying nonthermal source with constant spectral index. Two other general classes of models are considered: intrinsic variability and extrinsic modulation.

Odell, S. L.↗
NASA NTRS1972

Spectral reflectance measurements of a virus host model

A technique has been developed to detect the characteristic spectral signatures of healthy and infected St. Augustine grass. It is possible to predict the coverage of the infected area provided ground truth coverage shows positive St. Augustine grass turf. Qualitative measurements from photographs of plants in the blue and red regions with polarization show that light reflected from healthy plants is more strongly polarized than that from diseased plants. Photographs taken through the blue Wratten 47 filter in conjuction with a polarizer show an excellent differentiation. A large photographic difference also appears in the red region. Much smaller differences were noted in the 540 to 550 nm region. Although the intensity in the near-IR region is much higher than the visible region of the spectrum, differences in the healthy and diseased plants' reflectance were quite small.

Toler, R. W.↗
NASA NTRS1972

Determination of thawing snow and ice surfaces using earth satellite data

The apparent differential spectral reflectance is reported as sensed by the imaging dissector camera system in the visible portion of the electromagnetic spectrum and by the high resolution infrared radiometer in the near-IR portion of the electromagnetic spectrum. Both instruments were aboard the Nimbus 3 satellite.

Wiesnet, D. R.↗
NASA NTRS1972

Effect of simulated space radiation on selected optical materials.

The effect of simulated Nimbus spacecraft orbital (1100 km, circular, and polar) radiation on wide-band-pass glass filters, narrow-bandpass thin-film interference filters, and several fused silicas was determined by transmittance measurements over the 200-3400-nm wavelength region. No changes were observed in the filters, which were shielded with fused silica during irradiation, after exposure to a 1-yr equivalent orbital dose of electrons, nor were changes observed in the fused silicas after the same electron exposure plus a 1-yr equivalent dose of protons. Exposure to a 1/2-yr equivalent dose of solar uv radiation, however, caused a significant degradation in the transmittance of two uv-transmitting interference filters but had no effect on two colored glass filters that transmitted in the visible and near-ir regions. As a result of the uv exposure, the fused silicas exhibited losses of several percent over the 200-300-nm wavelength region.

Nicoletta, C. A.↗
NASA NTRS1973

ERTS-1 observes algal blooms in Lake Erie and Utah Lake

During late summer when the surface waters of Lake Erie reach their maximum temperature an algal bloom is likely to develop. Such phenomena have been noticed on other shallow lakes using ERTS-1 and characterize eutrophic conditions. The concentration of the algae into long streamers provides additional information on surface circulations. To augment the ERTS-1 MSS data of Lake Erie an aircraft was flown to provide correlative thermal-IR and additional multiband photographs. The algal bloom is highly absorptive in the visible wavelengths but reverses contrast with the surrounding water in the near-IR bands. The absorption of shortwave energy heats the dark brown algal mass, providing a hot surface target for the thermal-IR scanner.

Strong, A. E.↗
NASA NTRS1973

Asteroid spectral reflectivities.

We measured spectral reflectivities (0.3-1.1 micron) for 32 asteroids. There are at least 14 different curve types. Common types are: (a) reddish curves with 10% absorptions near 0.95 micron or beyond 1.0 micron, due to Fe(2+) in minerals such as pyroxenes; (b) flat curves in the visible and near-IR with sharp decreases in the UV and (c) flat curves even into the UV. Several asteroids show probable color variations with rotation, especially 6 Hebe. A sample of 102 asteroids with reliably known colors is derived from the reflectivities and from earlier colorimetry. Several correlations of colors and spectral curve types with orbital and physical parameters are examined: (1) asteroids with large aphelia have flat reflectivities while those with small perihelia are mostly reddish, (2) curve types show evidence for clustering on an a vs e plot, with 0.95 micron bands occuring mainly for Mars-approaching asteroids, (3) no strong correlation exists between color and either proper eccentricity or proper inclination.

Chapman, C. R.↗
NASA NTRS1974

Study to develop improved spacecraft snow survey methods using Skylab/EREP data

The author has identified the following significant results. A segment of the interim S192 film product from the SL-2 mission has been examined. The film covers the White Mountains area near the California-Nevada border and contains useable data for spectral bands: band 3, band 7, band 9, and band 11. Whereas the snow surface exhibits wide variations in reflectance, no significant change in the reflectance of the clouds occurs over the spectral range of these four bands. In band 11 the clouds appear white and snow appears black; in the band 3 data, both the clouds and the snow appear white. Two potential applications are possible, based on these results. First, because the reflectance of the snow surface in the band 9 data is much lower at the lower elevation terrain of the White Mountains, it appears that the drop in reflectance in the near-IR portion of the spectrum may be related to the wetness of the snow surface. Secondly, the complete reversal in reflectance that is observed in band 11 data indicates that in this portion of the spectrum snow surfaces have a low reflectance regardless of the condition of the snow. Because clouds do not exhibit a similar drop in reflectance, measurements in this spectral band have potential use for automatically distinguishing snow from clouds.

Barnes, J. C.↗
NASA NTRS1974

The application of ERTS imagery to monitoring Arctic sea ice

The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

Barnes, J. C.↗
NASA NTRS1974

Mariner-9 based simulation of radiative convective temperature changes in the Martian dust-laden atmosphere-soil system

A numerical simulation of radiative, conductive, and convective heat transfer of the Martian dust-laden atmosphere-soil system is presented with particular emphasis given to heating/cooling in regions of sharp variation in temperature or absorption and its resultant impact on outgoing planetary spectral radiance, as measured by the Mariner 9 IRIS. Thermal coupling between the ground and atmospheric subsystems is modeled by the total heat flux balance at the interface. In the simulation procedure, local thermodynamic equilibrium (LTE) is assumed, and a combined strong-weak line transmission function permits short- and long-range exchanges of energy from the surface toward space. Direct absorption of insolation in the near-IR bands by both silicate dust and CO2 is incorporated.

Dannevik, W. P.↗
NASA NTRS1975

An ERTS-1 investigation for Lake Ontario and its basin

The author has identified the following significant results. Methods of manual, semi-automatic, and automatic (computer) data processing were evaluated, as were the requirements for spatial physiographic and limnological information. The coupling of specially processed ERTS data with simulation models of the watershed precipitation/runoff process provides potential for water resources management. Optimal and full use of the data requires a mix of data processing and analysis techniques, including single band editing, two band ratios, and multiband combinations. A combination of maximum likelihood ratio and near-IR/red band ratio processing was found to be particularly useful.

Polcyn, F. C.↗
NASA NTRS1974

Observational constraints on model atmospheres for Uranus and Neptune

We have re-examined the visible and near-IR regions of the spectra of Uranus and Neptune to provide additional data for constructing atmospheric models. We find that a true continuum exists only at wavelengths below 4700 A, that the 6420 A absorption previously attributed to hydrogen is probably caused by methane, that there is no evidence for ammonia, ethylene or ethane absorptions in our spectra, and that the abundance of methane is probably much higher than previous estimates suggest. This last finding implies that the value of H/C in the atmospheres of both planets is much less than 1/10 the solar (or Jovian) value. Clear, Rayleigh-scattering model atmospheres are not compatible with the observations, but more work is needed to establish viable alternatives.

Encrenaz, T.↗
NASA NTRS1975

Silicon solid/state linear arrays for multispectral high resolution imaging systems

Solid-state, electronically scanned, linear detector arrays are now available which can be used in a pushbroom scan mode imaging system for high-resolution multispectral earth resource survey applications. These arrays provide high performance in the visible to near-IR region. Two performance criteria must be assessed in the choice of a detector array: signal-to-noise ratio and spectral response. Consideration of diffraction limitations shows that optics size cannot be significantly reduced by using very low-noise detectors. The required spectral response for a viable detector array should not have spectral ripples that cause a low-level, but significant, error in the detected effective reflectance of the target.

Thompson, L. L.↗
NASA NTRS1975

Near-infrared spectrophotometry of Titan

Several unusual features in the near-IR spectrum of Titan are examined. Observations during four apparitions establish the reality of the S(1) absorption at 8150.7 A, but the existence of the S(O) absorption at 8272.7 A will require further sightings to become definitively established. These two features are particularly important, as they bear on the abundance of H2 in Titan's atmosphere.

Trafton, L. M.↗
NASA NTRS1975

Surface properties of asteroids - A synthesis of polarimetry, radiometry, and spectrophotometry

Surface compositions of 110 asteroids are analyzed using data obtained by polarimetry and visible and near-IR spectrophotometry. A comparison of albedos and diameters determined by polarimetry and radiometry indicates that a slight upward revision of the radiometric albedo scale is necessary. Reliable adopted albedos and diameters are presented for 56 objects, and rough diameters are obtained for 52 additional objects. More than 90% of the asteroids are shown to fall into two broad groups (C and S) which are compositionally similar to carbonaceous and stony meteorites, respectively. C-type asteroids are found to predominate in the asteroid belt, and the largest of these (Ceres, Pallas, Hygiea, Davida) may be metamorphosed. It is shown that Vesta may be the only differentiated asteroid remaining intact in the belt. The results support the conclusions that asteroids and meteorites have similar classes of mineral assemblages, but the distribution of asteroid types contrasts with the distribution of major meteorite types found on earth.

Chapman, C. R.↗
NASA NTRS1975

Mass of the grazing fireball of August 1972

It is noted that the mass of the August 1972 meteoroid has been estimated to be of the order of one billion grams, based on the magnitude of its near-IR and visible radiation. In the present letter, published velocities and altitudes are analyzed from the viewpoint of momentum considerations. It is shown that the meteoroid mass was about 1000 times smaller than that deduced from the luminosity data.

Caulk, H. M.↗
NASA NTRS1976

Thermal inertia imaging - A new geologic mapping tool

A thermal model of the earth's surface has been developed and used to determine the thermal inertia of a test site in the Mojave Desert, California. The model, which includes meteorological heating terms as well as radiation and conduction heating terms, is used with remotely sensed surface temperature and reflectance data to determine the thermal inertia of the surface materials at the test site. The thermal inertia is displayed in image form, and can aid in the differentiation of the various lithologic materials in the test site. Since this thermal property is representative of the upper several cm of the surface, it complements visible and reflected near-IR image data.

Kahle, A. B.↗