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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Laser Range and Bearing Finder with No Moving Parts

A proposed laser-based instrument would quickly measure the approximate distance and approximate direction to the closest target within its field of view. The instrument would not contain any moving parts and its mode of operation would not entail scanning over of its field of view. Typically, the instrument would be used to locate a target at a distance on the order of meters to kilometers. The instrument would be best suited for use in an uncluttered setting in which the target is the only or, at worst, the closest object in the vicinity; for example, it could be used aboard an aircraft to detect and track another aircraft flying nearby. The proposed instrument would include a conventional time-of-flight or echo-phase-shift laser range finder, but unlike most other range finders, this one would not generate a narrow cylindrical laser beam; instead, it would generate a conical laser beam spanning the field of view. The instrument would also include a quadrant detector, optics to focus the light returning from the target onto the quadrant detector, and circuitry to synchronize the acquisition of the quadrant-detector output with the arrival of laser light returning from the nearest target. A quadrant detector constantly gathers information from the entire field of view, without scanning; its output is a direct measure of the position of the target-return light spot on the focal plane and is thus a measure of the direction to the target. The instrument should be able to operate at a repetition rate high enough to enable it to track a rapidly moving target. Of course, a target that is not sufficiently reflective could not be located by this instrument. Preferably, retroreflectors should be attached to the target to make it sufficiently reflective.

Bryan, Thomas C.↗
NASA NTRS1999

Development of the Double Etalon Fabry-Perot Interferometer for Determining Total and Tropospheric Ozone Concentrations

Measuring and understanding the distribution of ozone through the lower levels of Earth's atmosphere are high priorities in global change and climate research. Of particular interest now is the global distribution of ozone in the upper troposphere and lower stratosphere. Global coverage of the stratospheric ozone is feasible only via remote sensing instruments on a space-based platform. And though extensive monitoring tropospheric ozone is possible using instruments flown aboard conventional aircraft, a space-based system would be significantly less costly and provide information over a much broader area and produce more uniform coverage. Here we describe the prototype of an instrument being developed to monitor, from an orbiting spacecraft, the ozone found in Earth's upper troposphere and lower stratosphere. Our new spectrometer is an infrared Fabry-Perot interferometer which uses two synchrounously tuned etalons: a high resolution narrow band device and a lower resolution broader band filtering etalon. The prototype is a scanning device making use of nearly collimated input radiation and a single element detector. As presently configured, it is capable of providing a resolution better than 0.07/cm with a spectral band width approximately 5/cm wide and centered at 1054.7/cm. For the future space-based emission device a modification of the the prototype was to be made to employ innovative circle-to-line detector optics, those developed or in development at UM/SPRL, and a focal plane array detector. These enhancements would enable a simultaneous recording of the entire spectral range of interest, but with simple detection electronics and a significant gain in signal-to-noise over that of the scanning version.

Cook, William↗
NASA NTRSDate not supplied

A Decade of NASA Strategic Astrophysics Technology Investments: Technology Maturation, Infusion, and Other Benefits

NASA’s Astrophysics Division (APD) funds development of cutting-edge technology to enable its missions to achieve ambitious and groundbreaking science goals. These technology development efforts are managed by the Physics of the Cosmos (PCOS), Cosmic Origins (COR), and Exoplanet Exploration (ExE) Programs. The NASA Strategic Astrophysics Technology (SAT) Program was established in 2009 as a new technology maturation program to fill the gap in the Technology Readiness Level (TRL) range from 3 to 6. Since program inception, 100 SAT grants have been openly competed and awarded, along with dozens of direct-funded projects, leading to a host of technologies advancing their TRLs and/or being infused into space and suborbital missions and ground-based projects. We present the portfolio distribution in terms of specific technology areas addressed, including optics, detectors, coatings, coronagraphs, starshades, lasers, electronics, cooling systems, and micro-thruster subsystems. We show an analysis of the rate of TRL advances, infusion success stories, and other benefits such as training the future astrophysics workforce, including students and postdoctoral fellows hired by projects. Finally, we present APD’s current strategic technology maturation priorities for investment, enabling a range of future strategic astrophysics missions

NASA, astrophysics, technology development, optics↗
NASA NTRS2017

Hemispherical Optical Dome for Underwater Communication

For many years, acoustic systems have been used as the primary method for underwater communication; however, the data transfer rate of such systems is low because sound propagates slowly through the water. A higher throughput can be achieved using visible light to transmit data underwater. The first issue with using this approach is that there is generally a large loss of the light signal due to scattering and absorption in water even though there is an optimal wavelength for transmission in the blue or green wavelengths of the visible spectrum. The second issue is that a simple system consisting only of a highly directional source transmitter and small optical detector receiver has a very narrow field of view. The goal of this project is to improve an optical, underwater communication system by increasing the effective field of view of the receiving optics. To this end, we make two changes to the simple system: (1) An optical dome was added near the receiver. An array of lenses is placed radially on the surface of the dome, reminiscent of the compound eye of an insect. The lenses make the source and detector planes conjugate, and each lens adds a new region of the source plane to the instrument's total field of view. (2) The receiver was expanded to include multiple photodiodes. With these two changes, the receiver has much more tolerance to misalignments (in position and angle) of the transmitter.Two versions of the optical dome (with 6 and 8 diameters) were designed using the CREO CAD software and modeled using the CODE V optical design software. A series of these transparent hemispherical domes, with both design diameters, were manufactured using a 5-axis mill. The prototype was then retrofitted with lenses and compared with the computer-generated model to demonstrate the effectiveness of this solution. This work shows the dome design improves the optical field of view of the underwater communication system considerably. Furthermore, with the experimental test results, a geometric optimization model was derived providing insights to the design performance limits.

Design↗
NASA NTRS1993

Micro-optics technology and sensor systems applications

The current generation of electro-optical sensors utilizing refractive and reflective optical elements require sophisticated, complex, and expensive designs. Advanced-technology-based electro-optical sensors of minimum size and weight require miniaturization of optical, electrical, and mechanical devices with an increasing trend toward integration of various components. Micro-optics technology has the potential in a number of areas to simplify optical design with improved performance. This includes internally cooled apertures, hybrid optical design, microlenses, dispersive multicolor microlenses, active dither, electronically controlled optical beam steer, and microscopic integration of micro-optics, detectors, and signal processing layers. This paper describes our approach to the development of micro-optics technology with our main emphasis for sensors applications.

Gal, George↗
NASA NTRS2012

Optical multi-species gas monitoring sensor and system

The system includes at least one light source generating light energy having a corresponding wavelength. The system's sensor is based on an optical interferometer that receives light energy from each light source. The interferometer includes a free-space optical path disposed in an environment of interest. The system's sensor includes an optical device disposed in the optical path that causes light energy of a first selected wavelength to continue traversing the optical path whereas light energy of at least one second selected wavelength is directed away from the optical path. The interferometer generates an interference between the light energy of the first selected wavelength so-traversing the optical path with the light energy at the corresponding wavelength incident on the optical interferometer. A first optical detector detects the interference. At least one second detector detects the light energy at the at least one second selected wavelength directed away from the optical path.

Polzin, Kurt A.↗
NASA NTRS1980

Plasma Spray System

Computer aided, fully-automatic TRW system sprays very hot plasma onto a turbine blade. Composed of gas into which metallic and ceramic powders have been injected, the plasma forms a two-layer coating which insulates the blade. Critical part of operation is controlling the thickness of the deposit which is measured in thousandths of an inch. This is accomplished by an optical detector which illuminates spots at various locations on the blade and determines thickness by measuring the light reflections. Optical sensor monitors spraying process until precise thickness is attained, then computer halts the spraying.

Source record↗
NASA NTRS1982

Real-time optical synthetic aperture radar /SAR/ processor

A description is given of a real-time optical synthetic aperture radar (SAR). The processor employs an acoustooptic device as the input electronic-to-optical transducer and a CCD camera that serves as the optical detector and simultaneously performs the focusing of the SAR image in the azimuth direction. The performance criteria of the optical processor that are discussed include azimuth resolution, image size in azimuth, range resolution, image size in range, flexibility, and dynamic range.

Psaltis, D.↗
NASA NTRS1999

Coherent Doppler Wind Lidar Technology for Space Based Wind Measurements Including SPARCLE

It has been over 30 years since coherent lidar systems first measured wind velocity, and over 20 years since the "ultimate application" of measuring Earth's winds from space was conceived. Coherent or heterodyne optical detection involves the combination (or mixing) of the returned optical field with a local oscillator (LO) laser's optical field on the optical detector. This detection technique yields the benefits of dramatically improved signal-to-noise ratios; insensitivity to detector noise, background light and multiply scattered light; reduction of the returned signal's dynamic range; and preservation of the optical signal spectrum for electronic and computer processing. (Note that lidar systems are also referred to as optical radar, laser radar, and LADAR systems.) Many individuals, agencies, and countries have pursued the goal of space-based wind measurements through technology development, experiments, field campaigns and studies.

Kavaya, Michael J.↗
NASA NTRS1977

Gregorian all-reflective optical system

An optical heterodyne receiver comprises a system of reflectors forming a folded Gregorian configuration for collecting a signal beam, and an optical detector located at the focus of the system. A paraboloidal primary reflector and an elipsoidal secondary reflector face each other on an optical axis with the focus of the secondary reflector coinciding with the focus of the primary reflector. An auxiliary laser generates a local oscillator beam that is combined with the signal beam after the signal beam emerges from the exit pupil (which is also the aperture stop) of the system, and the resultant is impinged on the detector. A pair of image motion compensators is located as close to the exit pupil as possible for aligning off-axis inputs to the detector.

King, W. L.↗
NASA NTRS1999

Detector for Particle Surface Contamination

A system and method for detecting and quantizing particle fallout contamination particles which are collected on a transparent disk or other surface employs an optical detector, such as a CCD camera, to obtain images of the disk and a computer for analyzing the images. From the images, the computer detects, counts and sizes particles collected on the disk The computer also determines, through comparison to previously analyzed images, the particle fallout rate, and generates an alarm or other indication if the rate exceeds a maximum allowable value. The detector and disk are disposed in a housing having an aperture formed therein for defining the area on the surface of the disk which is exposed to the particle fallout. A light source is provided for evenly illuminating the disk. A first drive motor slowly rotates the disk to increase the amount of its surface area which is exposed through the aperture to the particle fallout. A second motor is also provided for incrementally scanning the disk in a radial direction back and forth over the camera so that the camera eventually obtains images of the entire surface of the disk which is exposed to the particle fallout.

Mogan, Paul A.↗
NASA NTRS2009

Fundamental Limits on the Imaging and Polarisation Properties of Far-Infrared Detectors

Far-infrared bolometric detectors are used extensively in ground-based and space-borne astronomy, and thus it is important to understand their optical behaviour precisely. We have studied the intensity and polarisation response of free-space bolometers, and shown that when the size of the absorber is reduced below a wavelength, the response changes from being that of a classical optical detector to that of a few-mode antenna. We have calculated the modal content of the reception patterns, and found that for any volumetric detector having a side length of less than a wavelength, three magnetic and three electric dipoles characterize the behaviour. The size of the absorber merely determines the relative strengths of the contributions. The same formalism can be applied to thin-film absorbers, where the induced current is forced to flow in a plane. In this case, one magnetic and two electric dipoles characterize the behaviour. The ability to model easily the intensity, polarisation, and straylight characteristics of electrically-small detectors will be of great value when designing high-performance polarimetric imaging arrays.

Thomas, Christopher N.↗
NASA NTRS1988

Characterization of a graphite epoxy optical bench during thermal vacuum cycling

In-situ monitoring of the Wide-Field/Planetary Camera, a Hubble Space Telescope science instrument, was performed in a vacuum environment to better understand the formation of ice on cooled optical detectors. Several diagnostic instruments were mounted on an access plate to view the interior of the instrument housing and the graphite epoxy optical bench. The instrumentation chosen and the rationale for choosing the instrumentation are discussed. In addition, the performance of the instrumentation during monitoring operations is discussed.

Hansen, Patricia A.↗
NASA NTRS1992

Condensation Of Volatile Contaminant In An Instrument

Report describes investigation of deposition of contaminant of cooled optical detectors in Wide-Field/Planetary Camera (WF/PC), an instrument in Hubble Space Telescope. To understand phenomenon, initially thought to be deposition of water from graphite/epoxy optical-bench material in instrument, researchers mounted several diagnostic instruments on access plate to monitor interior of WF/PC housing and optical bench. Temperature-controlled quartz-crystal microbalance (TQCM) measures adsorbed and desorbed volatile condensible material on surfaces in WF/PC.

Hansen, Patricia A.↗
NASA NTRS1972

Observability of high altitude atmospheric scattering layers

The observability of high altitude aerosol and atmospheric scattering layers by a satellite-mounted optical detector was considered. In particular the detectability of a 50 km layer with a wide-angle receiver was investigated. It was found that a layer possessing an optical depth greater than approximately 0.0002 at 3000 A (i.e. strong enough to affect BUV measurements of ozone) should be detectable with such an instrument provided that the system can be constructed so as to be sensitive to a signal of only 0.0001 of the sunlight directly incident on the instrument. However it was concluded that a narrow field-of-view satellite-mounted telescope used to scan the earth's horizon has a more general applicability for the detection of high altitude aerosol layers.

Cunnold, D. M.↗
NASA NTRS1981

Monolithically integrated active optical devices

Considerations relevant to the monolithic integration of optical detectors, lasers, and modulators with high speed amplifiers are discussed. Some design considerations for representative subsystems in the GaAs-AlGaAs and GaInAs-InP materials systems are described. Results of a detailed numerical design of an electro-optical birefringent filter for monolithic integration with a laser diode is described, and early experimental results on monolithic integration of broadband MESFET amplifiers with photoconductive detectors are reported.

Ballantyne, J.↗
NASA NTRS2000

Adaptive Detector Arrays for Optical Communications Receivers

The structure of an optimal adaptive array receiver for ground-based optical communications is described and its performance investigated. Kolmogorov phase screen simulations are used to model the sample functions of the focal-plane signal distribution due to turbulence and to generate realistic spatial distributions of the received optical field. This novel array detector concept reduces interference from background radiation by effectively assigning higher confidence levels at each instant of time to those detector elements that contain significant signal energy and suppressing those that do not. A simpler suboptimum structure that replaces the continuous weighting function of the optimal receiver by a hard decision on the selection of the signal detector elements also is described and evaluated. Approximations and bounds to the error probability are derived and compared with the exact calculations and receiver simulation results. It is shown that, for photon-counting receivers observing Poisson-distributed signals, performance improvements of approximately 5 dB can be obtained over conventional single-detector photon-counting receivers, when operating in high background environments.

Vilnrotter, V.↗