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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 397 records · Page 22
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NASA NTRS1972

Extreme-ultraviolet emission from solar prominences.

Spectra and spectroheliograms of prominences have been obtained at wavelengths of 300 to 1400 A from instruments aboard the OSO 4 and OSO 6 spacecraft. Quiescent prominences appear in emission above the limb for all strong lines formed at temperatures below 300,000 K, but not at higher temperatures. The gas pressure in the 100,000-K transition zone around prominences is approximately equal to that in the cooler (6500 K) central regions. The temperature and the hydrogen ground-state departure coefficient in the central regions are determined from the Lyman-continuum spectrum. Prominences on the disk (filaments) are visible in absorption in many lines, especially those at wavelengths below the hydrogen Lyman limit at 912 A.

Noyes, R. W.↗
NASA NTRS1974

Dynamics of plankton populations in upwelling areas

Recent investigations of the upwelling area along the NW Coast of Africa which include studies with satellites are discussed. The detection of patchiness in temperature and plankton distribution in the upwelling area is of special interest because they can be investigated from space synoptically with repeated coverage. The recent satellite missions provide recordings in the infrared region of the electromagnetic spectrum (EMR) as well as in the visible part. The information from those two parts of the EMR is useful for establishing the sea surface temperature and plankton distribution in upwelling areas. The temperature distribution as observed with infrared sensors and the patchiness in plankton patterns are discussed as observed with the most recent satellites, namely the Earth Resources Technology Satellite (ERTS) and NOAA-2.

Szekielda, K.↗
NASA NTRS1973

A filter-wheel solar radiometer for atmospheric transmission studies

A filter-wheel solar radiometer has been developed for monitoring the atmospheric optical depth at multiple narrow-wavelength intervals in the visible and near IR regions of the spectrum. Measurements of the direct solar radiations are converted to a digital format and stored in punched tape for eventual analysis by a computer. During stable clear weather condition, the instrument is capable of providing monochromatic optical depths to an estimated rms accuracy of 0.005.

Shaw, G. E.↗
NASA NTRS1974

An assessment of warm fog: Nucleation, control, and recommended research

A state-of-the-art survey is given of warm fog research which has been performed up to, and including, 1974. Topics covered are nucleation, growth, coalescence, fog structures and visibility, effects of surface films, drop size spectrum, optical properties, instrumentation, liquid water content, condensation nuclei. Included is a summary of all reported fog modification experiments. Additional data is provided on air flow, turbulence, a summary of recommendations on instruments to be developed for determining turbulence, air flow, etc., as well as recommendations of various fog research tasks which should be performed for a better understanding of fog microphysics.

Corrin, M. L.↗
NASA NTRS1976

The waveguide laser - A review

The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design and optimization of waveguide gas lasers.

Degnan, J. J.↗
NASA NTRS1977

Soyuz 22: New contribution to earth study from space

The mission of space flight Soyuz-22 was to develop new and improved methods and means for finding tthe Earth's natural resources from outer space to aid the economy. With the help of the new multispectral space camera, MKF-6, the cosmonauts were able to photograph selected areas of U.S.S.R. and the German Democratic Republic in 4 visible and 2 infrared regions of the spectrum. The MKF-6 can simultaneously photograph areas in 6 spectral regions and register both the natural electromagnetic radiation of surface objects and the solar radiation reflected by them.

Vedeshin, L. A.↗
NASA NTRS1979

Solar flares

The present paper deals with explosions in a magnetized solar plasma, known as flares, whose effects are seen throughout the electromagnetic spectrum, from gamma-rays through the visible and to the radio band. The diverse phenomena associated with flares are discussed, along with the physical mechanisms that have been advanced to explain them. The impact of solar flare research on the development of plasma physics and magnetohydrodynamics is noted. The rapid development of solar flare research during the past 20 years, owing to the availability of high-resolution images, detailed magnetic field measurements, and improved spectral data, is illustrated.

Rust, D. M.↗
NASA NTRS1979

Multisensor analysis of hydrologic features in the Wind River Range, Wyoming with emphasis on the SEASAT SAR

The author has identified the following significant results. Analysis of imagery obtained over west-central Wyoming indicates that Seasat SAR has capability for hydrologic mapping. Both the L-Band (Seasat) and the X-Band (aircraft) SAR imagery were useful for observing drainage detail. Streams have bright signatures on the SAR imagery because the riparian vegetation produces a rough surface and thus high radar returns. Lakes appear relatively bright on the Seasat image presumably in response to surface ripples and waves induced by wind action. SAR imagery did not reveal snow at either the 23.5 cm (L-Band) or 2.8 cm (X-Band) wavelengths. Comparing Seasat and X-Band aircraft SAR imagery to LANDSAT RBV imagery, U-2 photography, and topographic maps of the Wind River Range, it appears that the SAR data do not seem to provide as much hydrologic information as do the other sensors in the visible and near infrared portions of the spectrum.

Foster, J. L.↗
NASA NTRS1982

A plan for the characterization, calibration, and evaluation of LAPR-2

A new airborne Linear Array Pushbroom Radiometer (LAPR-II) was built. LAPR-II will use linear arrays of silicon detectors to acquire four channels of digital image data for spectral bands within the visible and near infrared portions of the spectrum (0.4 - 1.0 micrometers). The data will be quantized to 10 bits, and spectral filters for each channel will be changeable in flight. The instrument will initially be flown aboard a NASA/Wallops' aircraft, and off nadir pointing of LAPR-II will be possible. Together, the instrument and its platform will provide a flexible readily available source of digital image data for scientific experiments. If LAPR-II is to serve as a precise scientific instrument, the instrument's characteristics must be quantitatively described and the data must be calibrated with respect to absolute radiometric units. The LAPR-II is described and the work required to characterize the instrument's spectral response, radiometric response, and spatial resolution and to calibrate the response from the many detectors per array is outlined.

Ilrons, J. R.↗
NASA NTRS1983

Detectors for optical communications: A review

Detectors for optical communications in the visible and near infrared regions of the spectrum are reviewed. The three generic types of detectors described are: photomultipliers, photodiodes and avalanche photodiodes. Most of the information is applicable to other optical communications systems.

Katz, J.↗
NASA NTRS1984

LSS 4300 - A hot counterpart of Upsilon Sagittarii and KS Persei?

A number of recent observations indicate that the star LSS 4300 (HDE 320156) is a high-temperature analog of the hydrogen-deficient binaries Upsilon Sgr and KS Per. A preliminary model-atmosphere analysis based on high dispersion spectra obtained at Kitt Peak and Cerro Tololo yields Teff = 14,400 K, log (g) = 1.4, n(H)/n(He) = 0.003, and n(N)/n(C) = 20 for the visible component. The optical emission-line spectrum of LSS 4300 is nearly identical to that of Upsilon Sgr, including strong, broad H-alpha, Fe II, and forbidden Ca II emission; and JHKL photometry obtained at Cerr Tololo reveals an infrared excess nearly identical to that of Upsilon Sgr. It is suggested that LSS 4300, like Upsilon Sgr and KS Per, is a close binary system consisting of a helium supergiant of about 1 solar mass, which is undergoing its second mass loss, and a less luminous secondary, which is accreting matter from the primary.

Schoenberner, D.↗
NASA NTRS1982

Workshop on the Use of Future Multispectral Imaging Capabilities for Lithologic Mapping: Workshop summary

Improved orbital imaging capabilities from the standpoint of different scientific disciplines, such as geology, botany, hydrology, and geography were evaluated. A discussion on how geologists might exploit the anticipated measurement capabilities of future orbital imaging systems to discriminate and characterize different types of geologic materials exposed at the Earth's surface is presented. Principle objectives are to summarize past accomplishments in the use of multispectral imaging techniques for lithologic mapping; to identify critical gaps in earlier research efforts that currently limit the ability to extract useful information about the physical and chemical characteristics of geological materials from orbital multispectral surveys; and to define major thresholds, resolution and sensitivity within the visible and infrared portions of the electromagnetic spectrum which, if achieved would result in significant improvement in our ability to discriminate and characterize different geological materials exposed at the Earth's surface.

Settle, M.↗
NASA NTRS1985

Potential applications of multipolarization SAR for pine plantation biomass estimation

This study was conducted as a part of the research tasks under the Radar Land Cover Analysis Program. The Radar Land Cover Analysis objective is, through utilization of multisensor data, to gain a basic understanding of the measurements and data characteristics in the visible-IR-microwave regions of the electromagnetic spectrum associated with specific surface features and cover types. Since the results of analysis of data acquired by Shuttle Imaging Radar (SIR-A) and LANDSAT Thematic Mapper (TM) over the study area were reported (NSTL/ERL Report No. 228, December 1984), this study focused on the analysis and evaluation of the L-band multipolarization airborne SAR data acquired over a southeastern pine forest scene. The data acquisition mission was flown on September 8 and 9, 1983. The HH, HV polarizations and the VV, VH polarizations were used on the first and the second day, respectively. Due to instrumentation difficulties, the digital recorder recorded only the second day's data. Because of this, only the VV and VH polarization data were used in this analysis. However, the HH and HV polarization images were available for visual comparison. It appears that SAR digital numbers correlate with the index of green biomass.

Wu, S. T.↗
NASA NTRS1985

An assessment of the impact of spacecraft glow on the Hubble space telescope. Summary of existing observations and theory

Visible spacecraft glow was first observed on the Atmospheric Explorer spacecraft (AE-E) and studied in some detail with the Visible Airglow Experiment (VAE). The AE-E was a spin-stabilized spacecraft without thrusters at an altitude of 140 to 280 km. The VAE contained six visible wavelength photometers that measured a glow spectrum which: (1) rose steeply in the red, (2) decreased with a cos cubed PH1 dependence from pointing into the ram direction of the spacecraft orbital motion, and (3) decreased in intensity with increasing altitude with the same dependence as the measured atomic oxygen number atmospheric density (O) and not with the measured molecular nitrogen density (N sub 2). It is proposed that the glow is produced by chemical reactions on the spacecraft surface as it sweeps through the atmospheric O, with roughly 5-8 eV per O atom available for excitation from the orbital motion of the spacecraft. This glow may in principal be produced by any of a number of species, including molecular band emission from OH, NO, and NO2. An attempt is made to scale the observed glow to the Hubble space telescope.

Clarke, J. T.↗
NASA NTRS1987

The enigmatic object variable A in M33

Variable A is a very luminous (about -9.5 mag), highly unstable star in M33. In 1950, it was one of the visibly brightest stars in M33, with the spectrum of a very luminous F supergiant. It then rapidly declined in brightness by 3.5 mag, becoming faint and red after slowly increasing in brightness during the previous 50 yr. This paper reports current spectroscopy and visual and infrared photometry. Variable A is still faint and red and now has the spectrum of an M supergiant. It also has a large infrared excess and is today as bright at 10 microns as it was at its visual maximum in 1950. Its energy distribution, luminosities, and mass-loss rate, which is quite large at 0.0002 solar mass/yr, are discussed. Its present late-type spectrum is probably produced in a cool pseudophotosphere, and it is shedding its mass in a high-density, low-velocity wind. A possible explanation is presented for Variable A's bizarre behavior as a massive star near the critical limit to its stabilty for its initial mass and temperature, where the balance between the radiation pressure, turbulence, and gravity of its atmosphere is very uncertain.

Humphreys, Roberta M.↗
NASA NTRS1988

Comparison of high-altitude remote aircraft measurements with the radar structure of an Oklahoma thunderstorm - Implications for precipitation estimation from space

The present NASA ER-2 aircraft observations of an isolated group of thunderstorms over Oklahoma, encompassing passive radiometry in the visible, IR, and microwave portions of the spectrum obtained above the storm top, is compared with coincident data from two Doppler radars as well as aircraft-gathered in situ cloud top particle data. Reflectivity cores are found to be nearly colocated with cold anomalies in the microwave brightness temperature field. Theoretical considerations suggesting that microwave frequencies are sensitive to the deeper layer of large ice particles in the storm's convective region are supported.

Heymsfield, Gerald M.↗
NASA NTRS1992

Moderate resolution imaging spectroradiometer (MODIS) and observations of the land surface

The moderate resolution imaging spectroradiometer (MODIS) is a NASA facility instrument that is being designed for flight on the Earth Observing System (EOS) series of missions. It is designed to measure biophysical states and dynamics of the land, atmosphere, and ocean. Plans are required for use of other instruments that will be accompanying MODIS on the EOS missions, such as the High-Resolution Imaging Spectrometer (HIRIS) and the Multi-angle Imaging Spectro-Radiometer (MISR). The HIRIS instrument, a spectrometer operating in the visible to shortwave infrared parts of the spectrum, would be employed in combination with the MODIS to understand the impact of sampling the spectrum and the effects of land cover mixtures within the MODIS pixel. The MISR will help in understanding the effects of anisotropy in reflected solar radiation. Both instruments will work in combination with MODIS to better quantify the effects of the atmosphere on observations of surface properties.

Salomonson, V. V.↗
NASA NTRS1993

Optical flameout detector

A device has been developed which monitors the presence of a flame within a combustion chamber. The optical flameout detection system responds to gross changes in combustor light intensity, which is monitored in two spectral bands. A photomultiplier tube makes optical measurements in the ultraviolet portion of the spectrum, and a silicon photodiode covers the visible region. The detectors, located outside the combustion chamber, receive the light energy radiated from the combustion process through fiber optic probes designed to operate in a high pressure environment. The optical fibers are aimed diagonally through the center of the injector at the combustion chamber wall downstream of the injector. The probes observe events occurring within a narrow conical-shaped field of view so that the system can quickly detect longitudinal movement of the flame front away from the injector. If a change in intensity of the flame is detected, the fuel supply to the combustion chamber is shut off, limiting the amount of unburned fuel in the combustion chamber which could reignite.

Borg, Stephen E.↗