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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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

A search for optical flashes from the 'Perseus Flasher'

The results of an extended search for short-timescale optical flashes from a four square-degree area centered on the coordinates of the Perseus Flasher are reported. The photographed optical flash was of brightness mB = -1.7 and had a duration of roughly 0.5 s. In 70 hours of observation no celestial optical flashes were detected in the region of the Perseus Flasher to a limiting magnitude of 7.1 for a one-second flash. Neither X-ray nor optical flashes were seen. A survey of archived photographic images of the Perseus Flasher revealed no optical transients in over 700 hours of total exposure time to a limiting magnitude of mB about 4-5 for a one-second flash. Based on the ETC data base, possible terrestrial sources of optical flashes which might account for the phenomenon are discussed.

Vanderspek, Roland K.↗
NASA NTRS1986

Grazing incidence optics; Proceedings of the Meeting, Orlando, FL, Apr. 3, 4, 1986

Papers are presented on the diffraction-limited performance of grazing incidence optical systems; transverse ray aberrations of Wolter type 1 telescopes; hybrid X-ray telescope systems; surface characterization of grazing incidence optics in the extreme UV and X-ray regions; and the surface roughness properties of synchrotron radiation optics. Topics discussed include the simulation of free-abrasive grinding of grazing incidence mirrors with vertical-honing and flexible blades; mirrors for the Extreme Ultraviolet Explorer; the design and development of conical X-ray imaging mirrors; thermal loading considerations for synchrotron radiation mirrors; and grazing incidence optics for synchrotron radiation insertion-device beams. Consideration is given to the interpretation of glancing incidence scattering measurements; damage processes in short wavelength coated FEL optics; the replication of grain incidence optics; and the assembly and alignment of the Technology Mirror Assembly.

Osantowski, John F.↗
NASA NTRS1987

Highly Non-Linear Optical (NLO) organic crystals and films. Electrooptical organic materials

Devices employing nonlinear optics (NLO) hold great promise for important applications in integrated optics, optical information processing and telecommunications. Properly designed organics possess outstanding optical and electrooptical properties which will substantially advance many technologies including electrooptical switching, optical amplification for communications, and parallel processing for hybrid optical computers. A brief comparison of organic and inorganic materials is given.

Mcmanus, Samuel P.↗
NASA NTRS1987

Shuttle imaging spectrometer optics

This paper discusses the optical design and performance of the Shuttle Imaging Spectrometer (SISEX) optical system, which is being planned for the next generation of Earth remote sensing instruments. This optical system represents a new approach to remote sensing in which wide-field optics, dispersing elements, and area detector arrays are used in place of mechanical scanners, filters, and discrete detector elements or linear arrays. While the SISEX optical system is designed specifically for flight on Shuttle, the same optical approach is being used in the design of other remote sensing instruments, such as the High Resolution Imaging Spectrometer, which is expected to fly on the Earth Observing System.

Page, N. A.↗
NASA NTRS1989

State-of-the-art fiber optics for short distance frequency reference distribution

A number of recently developed fiber-optic components that hold the promise of unprecedented stability for passively stabilized frequency distribution links are characterized. These components include a fiber-optic transmitter, an optical isolator, and a new type of fiber-optic cable. A novel laser transmitter exhibits extremely low sensitivity to intensity and polarization changes of reflected light due to cable flexure. This virtually eliminates one of the shortcomings in previous laser transmitters. A high-isolation, low-loss optical isolator has been developed which also virtually eliminates laser sensitivity to changes in intensity and polarization of reflected light. A newly developed fiber has been tested. This fiber has a thermal coefficient of delay of less than 0.5 parts per million per deg C, nearly 20 times lower than the best coaxial hardline cable and 10 times lower than any previous fiber-optic cable. These components are highly suitable for distribution systems with short extent, such as within a Deep Space Communications Complex. Here, these new components are described and the test results presented.

Lutes, G. F.↗
NASA NTRS1990

Brief state-of-the-art review on optical communications for the NASA ISES workshop

The current state of the art of optical communications is briefly reviewed. This review covers NASA programs, DOD and other government agency programs, commercial aerospace programs, and foreign programs. Included is a brief summary of a recent NASA workshop on optical communications. The basic conclusions from all the program reviews is that optical communications is a technology ready to be accepted but needed to be demonstrated. Probably the most advanced and sophisticated optical communications system is the Laser Intersatellite Transmission Experiment (LITE) system developed for flight on the Advanced Communications Technology Satellite (ACTS). Optical communications technology is available for the applications of data communications at data rates in the under 300 MBits/sec for nearly all applications under 2 times GEO distances. Applications for low-earth orbiter (LEO) to ground will allow data rates in the multi-GBits/sec range. Higher data rates are limited by currently available laser power. Phased array lasers offer technology which should eliminate this problem. The major problem of cloud coverage can probably be eliminated by look ahead pointing, multiple ground stations, and knowledge of weather conditions to control the pointing. Most certainly, optical communications offer a new spectral region to relieve the RF bands and very high data communications rates that will be required in less than 10 years to solve the communications problems on Earth.

Hendricks, Herbert D.↗
NASA NTRS1990

Fiber optic smart structures and skins II; Proceedings of the Meeting, Boston, MA, Sept. 5-8, 1989

The present conference on embedded fiber-optics incorporating 'smart' structural systems and structural surfaces discusses topics in the nature and current status of university- and government-sponsored smart-structure development programs, manufacturing and cure-monitoring for composite smart structures, smart-structure damage assessment, smart-structure actuators, and smart-structure sensors and components. Attention is given to fiber-optic sensor selection, the optical properties of curing epoxies, the automated production of smart structures, damage-detection in composites with embedded fiber-optic interferometers, fiber-optic strain and impact sensors, dynamically-tunable smart composites, smart structures incorporating artificial neural networks, active structural acoustic control with smart structures, and fiber-optic shape sensing for flexible structures.

Udd, Eric↗
NASA NTRS1989

NASA/GSFC program in direct detection optical communications for intersatellite links

NASA-Goddard has undertaken the development of direct-detection optical communications for space applications at the Gbps data rate channel capability level. The primary challenges to optical communications designers lie in the development of reliable optical power sources, as well as of high performance pointing/acquisition/tracking systems required by the narrow widths of the transmitted optical beams. GaAlAs diodes and their arrays are currently the most attractive technology for optical transmitters; pioneering work has also been conducted on dichroic and grating techniques for combining the power of several laser diodes. Attention is given to the performance obtained for an optical link acquisition and submicroradian tracking/pointing system.

Fitzmaurice, M.↗
NASA NTRS1990

Optical and morphological properties of Cirrus clouds determined by the high spectral resolution lidar during FIRE

Cirrus clouds reflect incoming solar radiation and trap outgoing terrestrial radiation; therefore, accurate estimation of the global energy balance depends upon knowledge of the optical and physical properties of these clouds. Scattering and absorption by cirrus clouds affect measurements made by many satellite-borne and ground based remote sensors. Scattering of ambient light by the cloud, and thermal emissions from the cloud can increase measurement background noise. Multiple scattering processes can adversely affect the divergence of optical beams propagating through these clouds. Determination of the optical thickness and the vertical and horizontal extent of cirrus clouds is necessary to the evaluation of all of these effects. Lidar can be an effective tool for investigating these properties. During the FIRE cirrus IFO in Oct. to Nov. 1986, the High Spectral Resolution Lidar (HSRL) was operated from a rooftop site on the campus of the University of Wisconsin at Madison, Wisconsin. Approximately 124 hours of fall season data were acquired under a variety of cloud optical thickness conditions. Since the IFO, the HSRL data set was expanded by more than 63.5 hours of additional data acquired during all seasons. Measurements are presented for the range in optical thickness and backscattering phase function of the cirrus clouds, as well as contour maps of extinction corrected backscatter cross sections indicating cloud morphology. Color enhanced images of range-time indicator (RTI) displays a variety of cirrus clouds with approximately 30 sec time resolution are presented. The importance of extinction correction on the interpretation of cloud height and structure from lidar observations of optically thick cirrus are demonstrated.

Grund, Christian John↗
NASA NTRS1991

Digital optical computers at the optoelectronic computing systems center

The Digital Optical Computing Program within the National Science Foundation Engineering Research Center for Opto-electronic Computing Systems has as its specific goal research on optical computing architectures suitable for use at the highest possible speeds. The program can be targeted toward exploiting the time domain because other programs in the Center are pursuing research on parallel optical systems, exploiting optical interconnection and optical devices and materials. Using a general purpose computing architecture as the focus, we are developing design techniques, tools and architecture for operation at the speed of light limit. Experimental work is being done with the somewhat low speed components currently available but with architectures which will scale up in speed as faster devices are developed. The design algorithms and tools developed for a general purpose, stored program computer are being applied to other systems such as optimally controlled optical communication networks.

Jordan, Harry F.↗
NASA NTRS1991

Fiber optic frequency transfer link

A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.

Primas, Lori E.↗
NASA NTRS1990

Architecture for fiber-optic sensors and actuators in aircraft propulsion systems

This paper describes a design for fiber-optic sensing and control in advanced aircraft Electronic Engine Control (EEC). The recommended architecture is an on-engine EEC which contains electro-optic interface circuits for fiber-optic sensors. Size and weight are reduced by multiplexing arrays of functionally similar sensors on a pairs of optical fibers to common electro-optical interfaces. The architecture contains interfaces to seven sensor groups. Nine distinct fiber-optic sensor types were found to provide the sensing functions. Analysis revealed no strong discriminator (except reliability of laser diodes and remote electronics) on which to base a selection of preferred common interface type. A hardware test program is recommended to assess the relative maturity of the technologies and to determine real performance in the engine environment.

Glomb, W. L., Jr.↗
NASA NTRS1990

NASA Langley and AF RADC high-speed fiber optic transceiver program

NASA-Langley and the USAF Rome Air Development Center have been pursuing the development of military- and space-qualified fiber optic transceivers for a variety of ground-based, space-based, and general avionic applications. An initial development pursued a design called the multipurpose fiber optic transceiver (MFOX) and provided a family of fiber optic transceivers which operated up to 1 Gb/s. Currently, a second generation of high-speed fiber optic transceivers (HSFOX) is being developed. This design will utilize an all-integrated-circuits approach in order to develop a lighter-weight, smaller-size, and more efficient transceiver. The high-speed fiber optic transceiver will be military-and-space-operating in the 0.05-5 Gb/s data rate range. The initial results of tests, performance, and availability of commercial high-speed all-integrated-circuit chipsets for fiber-optic transceivers are discussed, as well as the performance of transceivers fabricated from these chipsets.

Hendricks, Herbert D.↗
NASA NTRS1992

Bulk Electro-Optical Polymer Component

Polymer serves in high-voltage sensors and laser-beam modulators. Electro-optical polymer of relatively low cost formed as bulk specimen from azo dye 4-(4-nitrophenylazo)-N-ethyl, N-2-hydroxyethylaniline, also known as Disperse Red 1 or DR1, and transparent epoxy. More stable than prior electro-optical polymers based on DR1 and poly(methylmethacrylate). If polymer were sandwiched between electrodes, it provides direct measurement of high voltage via electro-optical effect. Has significant nonlinear optical properties. Material useful in microelectronics, micro-optics, integrated optics, and testing of materials. Polymer withstands electric fields up to 120 kV/cm.

Gottsche, Allan↗
NASA NTRS1991

Sources of noise in magneto-optical readout

The various sources of noise which are often encountered in magneto-optical readout systems are analyzed. Although the focus is on magneto-optics, most sources of noise are common among the various optical recording systems and one can easily adapt the results to other media and systems. A description of the magneto-optical readout system under consideration is given, and the standard methods and the relevant terminology of signal and noise measurement are described. The characteristics of thermal noise, which originates in the electronic circuitry of the readout system, are described. The most fundamental of all sources of noise, the shot noise, is considered, and a detailed account of its statistical properties is given. Shot noise, which is due to random fluctuations in photon arrival times, is an ever-present noise in optical detection. Since the performance of magneto-optical recording devices in use today is approaching the limit imposed by the shot noise, it is important that the reader have a good grasp of this particular source of noise. A model for the laser noise is described, and measurement results which yield numerical values for the strength of the laser power fluctuations are presented. Spatial variations of the disk reflectivity and random depolarization phenomena also contribute to the overall level of noise in readout; these and related issues are treated. Numerical simulation results describing some of the more frequently encountered sources of noise which accompany the recorded waveform itself, namely, jitter noise and signal-amplitude fluctuation noise are presented.

Mansuripur, M.↗
NASA NTRS1991

Matching optics for Gaussian beams

A system of matching optics for Gaussian beams is described. The matching optics system is positioned between a light beam emitter (such as a laser) and the input optics of a second optics system whereby the output from the light beam emitter is converted into an optimum input for the succeeding parts of the second optical system. The matching optics arrangement includes the combination of a light beam emitter, such as a laser with a movable afocal lens pair (telescope) and a single movable lens placed in the laser's output beam. The single movable lens serves as an input to the telescope. If desired, a second lens, which may be fixed, is positioned in the beam before the adjustable lens to serve as an input processor to the movable lens. The system provides the ability to choose waist diameter and position independently and achieve the desired values with two simple adjustments not requiring iteration.

Gunter, William D.↗
NASA NTRS1991

Closed-loop motor control using high-speed fiber optics

A closed-loop control system for controlling the operation of one or more servo motors or other controllable devices is described. The system employs a fiber optics link immune to electromagnetic interference, for transmission of control signals from a controller or controllers at a remote station to the power electronics located in proximity to the motors or other devices at the local station. At the remote station the electrical control signals are time-multiplexed, converted to a formatted serial bit stream, and converted to light signals for transmission over a single fiber of the fiber optics link. At the local station, the received optical signals are reconstructed as electrical control signals for the controlled motors or other devices. At the local station, an encoder sensor linked to the driven device generates encoded feedback signals which provide information as to a condition of the controlled device. The encoded signals are placed in a formatted serial bit stream, multiplexed, and transmitted as optical signals over a second fiber of the fiber optic link which closes the control loop of the closed-loop motor controller. The encoded optical signals received at the remote station are demultiplexed, reconstructed and coupled to the controller(s) as electrical feedback signals.

Dawson, Reginald↗
NASA NTRS1991

The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure component

The first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.

Stacey, G. J.↗