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At least 307 records · Page 17

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NASA NTRS1973

Remote sensing technology - The 24-channel multispectral scanner.

The multispectral scanner system installed in the NASA C-130 aircraft for use in the Earth Observations Aircraft Program constitutes a 24-channel imaging spectrometer that senses electromagnetic energy in the spectral interval from .34 to 13 microns. Energy reflected or emitted from the terrain and system calibration sources is collected by a scan mirror, reflected into collecting optics, and brought to a focus in a plane containing a 0.09 inch square aperture. A dichroic optical element splits the energy which passes through the aperture into two wavelength bands (wavelengths above and below 2 microns). These wavelength bands are then dispersed spectrally into 24 distinct spectral bands by two grating spectrometers. The spectral intervals are transformed into electrical signals by separate detector-preamplifier combinations, and the signals are used as inputs to a video processor in an airborne electronics console. System operation and performance are described.

Hayre, H. S.↗

NASA NTRS1973

Atmospheric studies payloads

Several proposed Shuttle payloads for studying atmospheric phenomena and structure are discussed, with particular reference to a concept being developed for an optical facility. The payloads are put together of instruments both for in-situ measurements and for remote sensing of atmospheric emission, scattering, and absorption, using active and passive optical elements. Studies may include the artificial perturbation of the upper atmosphere with vapor releases or high powered UV lasers. The major areas of research in atmospheric physics are outlined, along with the parameters and phenomena of interest and the measurement techniques most frequently employed.

Hudson, R. D.↗

NASA NTRS1974

Real-time correction of atmospherically degraded telescope images through image sharpening

We present a new technique for the correction of atmospheric distortion in telescope images. Most of this distortion arises from a random phase variation of the incoming light across the telescope aperture. This variation limits the resolving power of even large telescopes to about one arc second. If the sharpness of the images is defined in a suitable way, this sharpness is maximized only when the phase distortion of the incoming light is zero. We present computer simulations of a simple feedback system in which active optical elements, set to maximize the sharpness, correct most of the atmospheric distortion. Photon statistics set the limiting magnitude of the object for which a practical feedback system can work. Details in a sixth magnitude object smaller than 0.1 sec of arc should be resolvable. The system can be conveniently employed within existing telescopes.

Muller, R. A.↗

NASA NTRS1977

Beam-splitter for infrared detection of pollutants

Germanium optical elements at proper tilt angles minimize effects of polarization and radiance variations of background scene. Energy-division ratio is less dependent on angle of incidence of entrance beam.

Massey, W. A.↗

NASA NTRS1977

Generation of a parallel X-ray beam and its use for testing collimators

A technique is described, by which a glass strip may be bent to match any curve of large radius of curvature, to a high degree of accuracy, so that it may be used as a glancing incidence X-ray or extreme ultraviolet optical element. The desired match is obtained by applying the optimum combination of end couples and by varying the cross-sectional moment of inertia along the length of the strip. A particular case, that of a parabola for use as a laboratory X-ray collimator, is considered in detail. The analysis predicts that a collimation of one or two arc seconds should be obtainable in practice, with simple and inexpensive apparatus. A prototype collimator to be used for the testing of space payloads using geometric (McGrath) collimators is described and laboratory results presented.

Underwood, J. H.↗

NASA NTRS1977

Bent glass optics

The paper describes how a glass strip may be bent to match any curve of large radius of curvature, to a high degree of accuracy, so that it may be used as a glancing incidence X-ray or extreme ultraviolet optical element. The desired match is obtained by applying a suitable combination of end couples and adjusting the cross-sectional moment of inertia along the length of the strip by varying its breadth. Two applications are described; a parabolic reflector for use as a laboratory X-ray collimator for testing mechanical collimators to be used in space instruments, and an elliptical reflector for point-to-point focussing. The latter device has been used for testing gratings in the X-ray and extreme ultraviolet (EUV) regions and for concentrating radiation on the entrance slit of a spectrometer, with a resultant gain in speed and resolution. It is suggested that the technique may have other laboratory and space applications, which are briefly described.

Underwood, J. H.↗

NASA NTRS1978

An ultra stable optical bench for the magnetic survey satellite

The Magsat optical bench has been designed and built to hold the alignment of five optical elements to deflections of 1-2 arcsec during orbital operation. The bench has been designed to withstand alignment changes during the launch and prestabilization phases of the mission. Severe weight constraints, in conjunction with the thermal and structural requirements, led to the choice of graphite-fiber-reinforced epoxy egg crate core and face sheets for the bench construction. Active temperature control was necessary to meet thermal deflection objectives, and novel kinematic mountings were required to prevent spacecraft bending from deflecting the bench.

Wingate, C. A., Jr.↗

NASA NTRS1979

Graphic design of pinhole cameras

The paper describes a graphic technique for the analysis and optimization of pinhole size and focal length. The technique is based on the use of the transfer function of optical elements described by Scott (1959) to construct the transfer function of a circular pinhole camera. This transfer function is the response of a component or system to a pattern of lines having a sinusoidally varying radiance at varying spatial frequencies. Some specific examples of graphic design are presented.

Edwards, H. B.↗

NASA NTRS1980

Optical considerations in infrared heterodyne spectrometer design

The optical design considerations for optimization of sensitivity, tunability, and versatility of an infrared heterodyne spectrometer are discussed using the GSFC CO2 laser heterodyne spectrometer optical front end as an example. Problems related to the coherent nature of the laser local oscillator beam (e.g., interference effects at edges of optical elements and at the beam combining beamsplitter) are described and proper beamsplitter design discussed. Optimum matching to the telescope is discussed. The severe effects of large central obscuration on the coherent telescope efficiency are described and steps to partially recover the lost system sensitivity are proposed. Measurements made with the GSFC 48 inch telescope (linear obscuration rate = 0.5) and the KPNO McMathe telescope (no obscuration) are given as examples.

Kostiuk, T.↗

NASA NTRS1979

Space optics; Proceedings of the Seminar, Huntsville, Ala., May 22-24, 1979

The seminar focused on infrared systems, the space telescope, new design for space astronomy, future earth resources systems, and planetary systems. Papers were presented on infrared astronomy satellite, infrared telescope on Spacelab 2, design alternatives for the Shuttle Infrared Telescope Facility, Spacelab 2 infrared telescope cryogenic system, geometrical theory of diffraction and telescope stray-light analysis, Space Telescope scientific instruments, faint-object spectrograph for the Space Telescope, light scattering from multilayer optics, bidirectional reflectance distribution function measurements of stray light suppression coatings for the Space Telescope, optical fabrication of a 60-in. mirror, interferogram analysis for space optics, nuclear-pumped lasers for space application, geophysical fluid flow experiment, coherent rays for optical astronomy in space, optical system with fiber-optical elements, and Pioneer-Venus solar flux radiometer.

Wyman, C. L.↗

NASA NTRS1980

The infrared radiometer on the sounder probe of the Pioneer Venus mission

The functional aspects of the Large Probe Infrared Radiometer Instrument are presented taking into account the experiment's objective to measure the net thermal flux as the Venus Probe descended into the planet's atmosphere, as well as to detect water vapor, cloud layers and their infrared opacity. The optical elements, including the detectors are described and a brief review of the instrument's calibration is given.

Boese, R. W.↗

NASA NTRS1980

Absorption coefficient instrument for turbid natural waters

The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.

Friedman, E.↗

NASA NTRS1980

Solar cell array design handbook - The principles and technology of photovoltaic energy conversion

Photovoltaic solar cell array design and technology for ground-based and space applications are discussed from the user's point of view. Solar array systems are described, with attention given to array concepts, historical development, applications and performance, and the analysis of array characteristics, circuits, components, performance and reliability is examined. Aspects of solar cell array design considered include the design process, photovoltaic system and detailed array design, and the design of array thermal, radiation shielding and electromagnetic components. Attention is then given to the characteristics and design of the separate components of solar arrays, including the solar cells, optical elements and mechanical elements, and the fabrication, testing, environmental conditions and effects and material properties of arrays and their components are discussed.

Rauschenbach, H. S.↗

NASA NTRS1982

Improved Magnetic-Field-Component Resolvers

New resolvers for vectorially summing outputs of aircraft-mounted magnetometers are lighter and more economical to fabricate than conventional electromagnetic resolvers. One resolver is based on potentiometric principles, the second uses polarization filters, and the third has variable-capacitance elements. Optical, capacitive and potentiometric devices have applications in aircraft navigation systems.

Garner, H. D.↗

NASA NTRS1981

Optical processing for landmark identification

A study of optical pattern recognition techniques, available components and airborne optical systems for use in landmark identification was conducted. A data base of imagery exhibiting multisensor, seasonal, snow and fog cover, exposure, and other differences was assembled. These were successfully processed in a scaling optical correlator using weighted matched spatial filter synthesis. Distinctive data classes were defined and a description of the data (with considerable input information and content information) emerged from this study. It has considerable merit with regard to the preprocessing needed and the image difference categories advanced. A optical pattern recognition airborne applications was developed, assembled and demontrated. It employed a laser diode light source and holographic optical elements in a new lensless matched spatial filter architecture with greatly reduced size and weight, as well as component positioning toleranced.

Casasent, D.↗

NASA NTRS1981

Optical Spatial integration methods for ambiguity function generation

A coherent optical spatial integration approach to ambiguity function generation is described. It uses one dimensional acousto-optic Bragg cells as input tranducers in conjunction with a space variant linear phase shifter, a passive optical element, to generate the two dimensional ambiguity function in one exposure. Results of a real time implementation of this system are shown.

Tamura, P. N.↗

NASA NTRS1982

Dish concentrators for solar thermal energy: Status and technology development

Point-focusing concentrators under consideration for solar thermal energy use are reviewed. These concentrators differ in such characteristics as optical configuration, optical materials, structure for support of the optical elements and of the receiver, mount, foundation, drive, controls and enclosure. Concentrator performance and cost are considered. Technology development is outlined, including wind loads and aerodynamics; precipitation, sand, and seismic considerations; and maintenance and cleaning.

Jaffe, L. D.↗

NASA NTRS1981

Secondary concentrators for parabolic dish solar thermal power systems

A variety of different concepts are currently being studied with the objective to lower the cost of parabolic mirrors and to provide alternatives. One of the considered approaches involves the use of compound concentrators. A compound solar concentrator is a concentrator in which the sunlight is reflected or refracted more than once. It consists of a primary mirror or lens, whose aperture determines the amount of sunlight gathered, and a smaller secondary mirror or lens. Additional small optical elements may also be incorporated. The possibilities and problems regarding a use of compound concentrators in parabolic dish systems are discussed. Attention is given to concentrating secondary lenses, secondary imaging and concentrating mirrors, conical secondary mirrors, compound elliptic secondary concentrating mirrors, and hyperbolic trumpet secondary concentrating mirrors.

Jaffe, L. D.↗