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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Limb brightening on Uranus - The visible spectrum

Results are presented for pinhole and slit narrowband photoelectric area-scanning photometry of the Uranus disk at eight central wavelengths ranging from 5600 to 7500 A. The observations were undertaken to detect limb brightening on the planet and to study the nature of its disk profile as a function of geometrical albedo. A coarse analysis of the results shows that the disk must exhibit limb brightening in the two CH4 bands at 6190 and 7300 A relative to all other wavebands investigated. Except for the two CH4 bands, the shapes and widths of the images are found to be essentially identical; point-spread-function data for all wavebands indicate no significant variation in the representative Gaussian l/e width with wavelength. A fine analysis of the data reveals absolute limb brightening in the 7300-A CH4 band and absolute limb darkening in the adjacent wavebands. These results are shown to be consistent with the hypothesis that clouds are absent from the visible atmosphere of Uranus.

Price, M. J.↗
NASA NTRS1976

An approach to improve management visibility within the procurement and financial group at Goldstone

Improvements in the operational efficiency of the data management systems at the Goldstone Deep Space Communications Complex (GDSCC) are discussed. This addresses the existing procurement and financial management data system at GDSCC, identifies management requirements for better visibility, describes a proposed computerized data management system, summarizes results to data, and identifies plans for future development.

Maiocco, F. R.↗
NASA NTRS1977

Visible and infrared imaging radiometers for ocean observations

The current status of visible and infrared sensors designed for the remote monitoring of the oceans is reviewed. Emphasis is placed on multichannel scanning radiometers that are either operational or under development. Present design practices and parameter constraints are discussed. Airborne sensor systems examined include the ocean color scanner and the ocean temperature scanner. The costal zone color scanner and advanced very high resolution radiometer are reviewed with emphasis on design specifications. Recent technological advances and their impact on sensor design are examined.

Barnes, W. L.↗
NASA NTRS1977

Skylab S191 visible-infrared spectrometer

The paper describes the S191 visible-infrared spectrometer of the Skylab Earth Resources Experiment Package - a manually pointed two-channel instrument operating in the reflective (0.4-2.5 micron) and thermal emissive (6-15 micron) regions. A sensor description is provided and attention is given to data quality in the short wavelength and thermal infrared regions.

Barnett, T. L.↗
NASA NTRS1977

Visible optical isolator using ZnSe

A compact Faraday effect optical isolator was constructed for visible wavelengths and tested at 5145 A. The nonreciprocal element of the isolator was polycrystalline zinc selenide placed in the magnetic field of a permanent magnet. For 5145 A the isolator had a 2.06-dB insertion loss and a 25.5-dB isolation. Indices of refraction and Verdet constants were measured for zinc selenide in the wavelength region from 4700 to 6300 A.

Wunderlich, J. A.↗
NASA NTRS1979

Instrument measures many optical properties in visible and IR

Electro-optical system measures reflectance, reflectance ratio, transmission, absorption, refractive index, and absorption coefficient in both visible and infrared (IR) spectral regions. System effectively combining capabilities of ellisometer, reflectometer, and spectrophotometer is expected to find application in environmental and material composition testing fields.

Batten, C. E.↗
NASA NTRS1977

Visible and infrared imaging radiometers for ocean observations

The technology of visible and infrared imaging sensors designed for the remote monitoring of the oceans is assessed. Emphasis is placed on multichannel scanning radiometers that are either operational or under development. Present design practices and parameter constraints are discussed. Airborne sensor systems examined include the Ocean Color Scanner (OCS) and the Ocean Temperature Scanner (OTS). The Coastal Zone Color Scanner (CZCS) and Advanced Very High Resolution Radiometer (AVHRR), are reviewed with emphasis on design specifications, expected completion, and anticipated performance. Finally, recent technology advances and their probable impact on sensor design are examined.

Barnes, W. L.↗
NASA NTRS1978

Study to determine operational and performance criteria for STOL aircraft operating in low visibility conditions

The operational and performance criteria for civil CTOL passenger-carrying airplanes landing in low visibilities depend upon the characteristics of the airplane, the nature and use of the ground and airborne guidance and control systems, and the geometry and lighting of the landing field. Based upon these criteria, FAA advisory circulars, airplane and equipment design characteristics, and airline operational and maintenance procedures were formulated. The documents are selected, described, and discussed in relationship to the potential low weather minima operation of STOL aircraft. An attempt is made to identify fundamental differences between CTOL and STOL aircraft characteristics which could impact upon existing CTOL documentation. Further study and/or flight experiments are recommended.

Gorham, J. A.↗
NASA NTRS1977

Conversion of visible light to electrical energy - Stable cadmium selenide photoelectrodes in aqueous electrolytes

Stabilization of n-type CdSe to photoanodic dissolution is reported. The stabilization is accomplished by the competitive oxidation of S(--) or S(n)(--) at the CdSe photoanode in an electrochemical cell. Such stabilized cells are shown to sustain the conversion of low energy (not less than 1.7 eV) visible light to electricity with good efficiency and no deterioration of the CdSe photoelectrode or of the electrolyte. The electrolyte undergoes no net chemical change because the oxidation occurring at the photoelectrode is reversed at the cathode. Conversion of monochromatic light at 633 nm to electricity is shown to be up to approximately 9% efficient with output potentials of approximately 0.4 V. Conversion of solar energy to electricity is estimated to be approximately 2% efficient.

Wrighton, M. S.↗
NASA NTRS1978

Physical properties of aerosols in Titan's atmosphere as deduced from visible observations

Analysis of the absolute value of Titan's albedo and its variation with increasing phase angle has yielded constraints on the optical properties and average particle size of the aerosols responsible for the scattering of visible light. The real index of refraction of the scattering material lies within the range 1.5 approximately less than nr approximately less than 2.0 and the average particle size is somewhere between 0.2 micrometer and 0.4 micrometer. The amount of limb darkening produced by these models leads to an occultation radius of approximately 2700 km.

Rages, K.↗
NASA NTRS1978

Visibility in aviation

An overview of the development of instrumental methods of making cloud height and visibility measurements is presented. The limitations of these measurements are discussed.

Douglas, C. O.↗
NASA NTRS1979

Visible flux variations across finite clouds

A radiative transfer model developed to computer visible flux variations across and within finite clouds of varying shapes is described. The technique has much of the versatility of Monte Carlo models, as well as the speed of the analytical finite cloud models.

Mosher, F. R.↗
NASA NTRS1979

Altered rock spectra in the visible and near infrared

The author has identified the following significant results. Visible and near-infrared (0.35 to 2.5 micron m) bidirectional reflection spectra recorded for a suite of well-characterized hydrothermally altered rock samples typically display well defined bands caused by both electronic and vibrational processes in the individual mineral constituents. Electronic transitions in the iron-bearing constituent minerals produce diagnostic minima near 0.43, 0.65, 0.85, and 0.93 micron m. Vibrational transitions in clay and water-bearing mineral constituents produce characteristic single or multiple features over limited spectral ranges near 1.4, 1.75, 1.9, 2.2, and 2.35 micron m. The most abundant feature-producing minerals present in these rocks are hematite, goethite, and alunite. Others frequently present are jarosite, kaolinite, potassium micas, pyrophyllite, montmorillonite, diaspore, and gypsum. The spectral region near 2.2 micron m is particularly important for detecting altered rocks by remote sensing.

Hunt, G. R.↗
NASA NTRS1978

Spectroscopy in the study of planetary atmospheres - Abundances from the visible region

Spectrophotometric studies of three molecular constituents - hydrogen, methane, and ammonia - identified in the visible region of the spectra of the outer planets are reviewed. The history of quadrupole line observations for hydrogen molecules and the significance of the HD molecule for the dipole spectrum are considered. Approaches to quantitative estimates of methane concentration in planetary atmospheres are explained, and the detection of ammonia in the atmospheres of Jupiter and Saturn is described.

Lutz, B. L.↗
NASA NTRS1978

Simultaneous visible and ultraviolet spectroscopy of stellar wind variability in Zeta Puppis

Spectra of He II 4686 A and H-alpha in Zeta Pup were obtained simultaneously with Copernicus ultraviolet scans of several P Cygni profiles in this O4 If supergiant with strong mass loss. The visible-wavelength data show significant variations in the profiles of both lines, consisting of doubling of the emission over times of less than a day. Recent theoretical calculations show that the observed profile variations in 4686 A can be produced by significant fluctuations in the wind density. The Copernicus data show less variability, although in one scan of the 1400-A Si IV doublet there appears to be a significant enhancement of the emission which may be correlated with one of the doublings observed in 4686 A and H-alpha, as though a density enhancement formed at low levels and then moved outward in the wind.

Wegner, G. A.↗
NASA NTRS1978

On the nature and visibility of crater-associated streaks on Mars

The paper considers Mariner 9 and Viking data that contradict Kuzmin's (1975) hypothesis that all crater-associated wind streaks on Mars are depositional and consist of unresolved barchan-like dunes. According to Kuzmin's hypothesis, any streak can appear either bright or dark relative to its surroundings depending on the sun's position. The spacecraft images, however, show examples of dark and light streaks visible at the same azimuth angle of the sun. Evidence that bright and dark streaks differ both in morphology and in character is considered. It is suggested that the common ragged dark streaks are probably erosion scars while most bright streaks probably represent accumulations of bright dust-storm fallout.

Veverka, J.↗
NASA NTRS1978

Plagioclase feldspars - Visible and near infrared diffuse reflectance spectra as applied to remote sensing

Visible and near IR diffuse reflectance spectra of plagioclase feldspars are characterized by absorption features caused by minor amounts of Fe(2+) that occur bound in the crystal structure. It is found that identification of terrestrial feldspars by remote sensing appears to be feasible for the compositional range An50 to An80, providing that other minerals do not mask the feldspar signatures. Determination of plagioclase composition using the wavelength of the Fe(2+) band may be possible for lunar samples, where the plagioclase can be assumed to be more calcic than An65.

Adams, J. B.↗
NASA NTRS1980

Head-up transition behavior of pilots during simulated low-visibility approaches

Each of 13 commercial pilots from four airlines flew a total of 108 manual flight director approaches in a moving base simulation of a medium-sized turbojet (95,000 lb gross weight) which had a day and night Redifon external scene. Three levels of runway visual range (RVR) (1,600; 2,400; and greater than 8,000 ft), three wind-shear profiles, nine ceiling heights, and continuous and intermittent visibility after initial breakout were tested. The results indicated that: (1) mean decision time ranged from 2 to 4.6 sec for ceilings under 380 ft across the three RVR conditions; (2) mean vertical distance traveled during the visual-cue assessment period was a relatively constant proportion below the existing ceiling; (3) a significant three way interaction in mean decision time between wind shear, day-night, and ceiling RVR variables occurred; (4) mean number of head-up transitions to VFR conditions after breakout ranged from 4.6 to 13.4 and increased as a function of ceiling and severity of wind shear; the typical duration of fixation out the window was 1.5 sec; and (5) subjective pilot ratings of controllability and precision of control as well as amount of skill, attention, or effort required to make the landing were influenced significantly by the wind shear, night conditions, and low breakout ceiling conditions.

Haines, R. F.↗