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Results for “lighting system performance”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Laboratory evaluation of Fecker and Loral optical IR PWI systems

A previous flight test of two electro-optical pilot warning indicators, using a flashing xenon strobe and silicon detectors as cooperative elements, pointed out several design deficiencies. The present laboratory evaluation program corrected these faults and calibrated the sensitivity of both systems in azimuth elevation and range. The laboratory tests were performed on an optical bench and consisted of three basic components: (1) a xenon strobe lamp whose output is monitored at the indicator detector to give pulse to pulse information on energy content at the receiver; (2) a strobe light attenuating optical system which is calibrated photometrically to provide simulated range; and (3) a positioning table on which the indicator system under study is mounted and which provides spatial location coordinates for all data points. The test results for both systems are tabulated.

Gorstein, M.↗
NASA NTRSDate not supplied

A Real-Time Optical Ground Receiver for Photon Starved Environments

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has developed a photon-counting optical ground receiver for pulse-position modulated signals. The real-time receiver system includes a fiber interconnect, superconducting nanowire single-photon detectors (SNSPDs), and a real-time field programmable gate array (FPGA) based receiver. The fiber interconnect and SNSPDs are implemented with two different configurations. In the first, a 7-channel few-mode fiber photonic lantern couples the light from the telescope to 7 single-pixel few-mode fiber coupled SNSPDs. In the second configuration, a few-mode fiber couples light to a 16-pixel monolithic SNSPD array. The real-time FPGA-based receiver performs combining of up to 16 SNSPD channels, symbol timing recovery, demodulation, and decoding. The system is scalable with data rates ranging from 20 Mbps to 267 Mbps. It is compliant with the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Standard. This standard will be used in NASA deep space and other low photon flux missions, such as in the Orion Artemis-2 Optical Communications System (O2O) demonstration, planned for the first crewed flight of Orion. This paper describes the scalable real-time optical receiver system and presents characterization test results.

optical communications↗
NASA NTRSDate not supplied

A Real-Time Optical Ground Receiver for Photon Starved Environments

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has developed a photon-counting optical ground receiver for pulse-position modulated signals. The real-time receiver system includes a fiber interconnect, superconducting nanowire single-photon detectors (SNSPDs), and a real-time field programmable gate array (FPGA) based receiver. The fiber interconnect and SNSPDs are implemented with two different configurations. In the first, a 7-channel few-mode fiber photonic lantern couples the light from the telescope to 7 single-pixel few-mode fiber coupled SNSPDs. In the second configuration, a few-mode fiber couples light to a 16-pixel monolithic SNSPD array. The real-time FPGA-based receiver performs combining of up to 16 SNSPD channels, symbol timing recovery, demodulation, and decoding. The system is scalable with data rates ranging from 20 Mbps to 267 Mbps. It is compliant with the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Standard. This standard will be used in NASA deep space and other low photon flux missions, such as in the Orion Artemis-2 Optical Communications System (O2O) demonstration, planned for the first crewed flight of Orion. This paper describes the scalable real-time optical receiver system and presents characterization test results.

optical communications↗
NASA NTRS1981

Operational considerations in utilization of microwave landing system approach and landing guidance

The characteristics and performance of MLS equipment utilized by the TCV B-737. Several classes of MLS service and approach procedures are discussed in light of TCV experience. Since the early uses of MLS involves procedures identical to ILS, most of the discussion is concerned with exploitation of MLS capabilities not possessed by ILS. Examples are given of how this could be done by using MLS to enhance the safety and utility of procedures presently in use for noise abatement. Some areas which require definition of new procedures and conventions are indicated.

White, W. F.↗
NASA NTRS2005

Performance Monitoring and Assessment of Neuro-Adaptive Controllers for Aerospace Applications Using a Bayesian Approach

Modem aircraft, UAVs, and robotic spacecraft pose substantial requirements on controllers in the light of ever increasing demands for reusability, affordability, and reliability. The individual systems (which are often nonlinear) must be controlled safely and reliably in environments where it is virtually impossible to analyze-ahead of time- all the important and possible scenarios and environmental factors. For example, system components (e.g., gyros, bearings of reaction wheels, valves) may deteriorate or break during autonomous UAV operation or long-lasting space missions, leading to a sudden, drastic change in vehicle performance. Manual repair or replacement is not an option in such cases. Instead, the system must be able to cope with equipment failure and deterioration. Controllability of the system must be retained as good as possible or re-established as fast as possible with a minimum of deactivation or shutdown of the system being controlled. In such situations the control engineer has to employ adaptive control systems that automatically sense and correct themselves whenever drastic disturbances and/or severe changes in the plant or environment occur.

Gupta, Pramod↗
NASA NTRS2015

How to Directly Image a Habitable Planet Around Alpha Centauri with a 30-45 cm Space Telescope

Several mission concepts are being studied to directly image planets around nearby stars. It is commonly thought that directly imaging a potentially habitable exoplanet around a Sun-like star requires space telescopes with apertures of at least 1m. A notable exception to this is Alpha Centauri (A and B), which is an extreme outlier among FGKM stars in terms of apparent habitable zone size: the habitable zones are approximately 3x wider in apparent size than around any other FGKM star. This enables a approximately 30-45cm visible light space telescope equipped with a modern high performance coronagraph or star shade to resolve the habitable zone at high contrast and directly image any potentially habitable planet that may exist in the system. The raw contrast requirements for such an instrument can be relaxed to 1e-8 if the mission spends 2 years collecting tens of thousands of images on the same target, enabling a factor of 500-1000 speckle suppression in post processing using a new technique called Orbital Difference Imaging (ODI). The raw light leak from both stars is controllable with a special wave front control algorithm known as Multi-Star Wave front Control (MSWC), which independently suppresses diffraction and aberrations from both stars using independent modes on the deformable mirror. This paper will present an analysis of the challenges involved with direct imaging of Alpha Centauri with a small telescope and how the above technologies are used together to solve them. We also show an example of a small coronagraphic mission concepts to take advantage of this opportunity called "ACESat: Alpha Centauri Exoplanet Satellite" submitted to NASA's small Explorer (SMEX) program in December of 2014.

exoplanets↗
NASA NTRS2006

Broadband Performance of TPF's High-contrast Imaging Testbed: Modeling and Simulations

The broadband performance of the high-contrast imaging testbed (HCIT) at JPL is investigated through optical modeling and simulations. The analytical tool is an optical simulation algorithm developed by combining the HCIT's optical model with a speckle-nulling algorithm that operates directly on coronagraphic images, an algorithm identical to the one currently being used on the HCIT to actively suppress scattered light via a deformable mirror. It is capable of performing full three-dimensional end-to-end near-field diffraction analysis on the HCIT's optical system. By conducting speckle-nulling optimization, we clarify the HCIT's capability and limitations in terms of its broadband contrast performance under various realistic conditions. Considered cases include non-ideal occulting masks, such as a mask with optical density and wavelength dependent parasitic phase-delay errors (i.e., a not band-limited occulting mask) and the one with an optical-density profile corresponding to a measured, non-standard profile, as well as the independently measured phase errors of all optics. Most of the information gathered on the HCIT's optical components through measurement and characterization over the last several years at JPL has been used in this analysis to make the predictions as accurate as possible. The best contrast values predicted so far by our simulations obtainable on the HCIT illuminated with a broadband light having a bandwidth of 80nm and centered at 800nm wavelength are Cm=1.1x10-8 (mean) and C4=4.9x10-8 (at 4(lamda)/D), respectively. In this paper we report our preliminary findings about the broadband light performance of the HCIT.

integrated modeling↗
NASA NTRS1986

Controlled Ecological Life Support Systems (CELSS) conceptual design option study

Results are given of a study to explore options for the development of a Controlled Ecological Life Support System (CELSS) for a future Space Station. In addition, study results will benefit the design of other facilities such as the Life Sciences Research Facility, a ground-based CELSS demonstrator, and will be useful in planning longer range missions such as a lunar base or manned Mars mission. The objectives were to develop weight and cost estimates for one CELSS module selected from a set of preliminary plant growth unit (PGU) design options. Eleven Space Station CELSS module conceptual PGU designs were reviewed, components and subsystems identified and a sensitivity analysis performed. Areas where insufficient data is available were identified and divided into the categories of biological research, engineering research, and technology development. Topics which receive significant attention are lighting systems for the PGU, the use of automation within the CELSS system, and electric power requirements. Other areas examined include plant harvesting and processing, crop mix analysis, air circulation and atmosphere contaminant flow subsystems, thermal control considerations, utility routing including accessibility and maintenance, and nutrient subsystem design.

Oleson, Melvin↗
NASA NTRS1998

Load Distribution in Transmissions "Split"

The transmission system of a helicopter must meet particularly critical requirements. It must transmit engine power to the rotor, at the same time ensuring a typical speed reduction of 60 to 1. It must also be safe, reliable, light, and reach a high level of performance while, at the same time, it must produce few vibrations and little noise. Helicopter transmissions have achieved high-level performances thanks to the combination of analyses, experiments, and the application of practical field experience. However, the new generation of helicopters will require transmission systems that are even safer, lighter, less noisy, and more reliable.

Krantz, Timothy L.↗
NASA NTRS1997

Effect of Display Color on Pilot Performance and Describing Functions

A study has been conducted with the full-spectrum, calligraphic, computer-generated display system to determine the effect of chromatic content of the visual display upon pilot performance during the landing approach maneuver. This study utilizes a new digital chromatic display system, which has previously been shown to improve the perceived fidelity of out-the-window display scenes, and presents the results of an experiment designed to determine the effects of display color content by the measurement of both vertical approach performance and pilot-describing functions. This method was selected to more fully explore the effects of visual color cues used by the pilot. Two types of landing approaches were made: dynamic and frozen range, with either a landing approach scene or a perspective array display. The landing approach scene was presented with either red runway lights and blue taxiway lights or with the colors reversed, and the perspective array with red lights, blue lights, or red and blue lights combined. The vertical performance measures obtained in this experiment indicated that the pilots performed best with the blue and red/blue displays. and worst with the red displays. The describing-function system analysis showed more variation with the red displays. The crossover frequencies were lowest with the red displays and highest with the combined red/blue displays, which provided the best overall tracking, performance. Describing-function performance measures, vertical performance measures, and pilot opinion support the hypothesis that specific colors in displays can influence the pilots' control characteristics during the final approach.

Chase, Wendell D.↗
NASA NTRS1979

Laser measuring system for wire-wrapped frame assemblies

The laser measuring system is designed to automatically measure and record the distances between small diameter wires on a wire wrapped grid frame assembly to an accuracy of 0.00635 mm (0.00025 in.). The system utilizes a helium-neon gas laser beam as the measuring instrument with a remote interferometer and retroreflector, a light source and photodetector to detect the wire positions, in conjunction with recording, display and printout units. The laser measuring system is utilized to perform precise automatic measurements for wire application machines or as an automatic feedback device for positioning wires and/or to adjust them for out of tolerance conditions.

Etzel, J. G.↗
NASA NTRS1994

Evaluation of visual acuity with Gen 3 night vision goggles

Using laboratory simulations, visual performance was measured at luminance and night vision imaging system (NVIS) radiance levels typically encountered in the natural nocturnal environment. Comparisons were made between visual performance with unaided vision and that observed with subjects using image intensification. An Amplified Night Vision Imaging System (ANVIS6) binocular image intensifier was used. Light levels available in the experiments (using video display technology and filters) were matched to those of reflecting objects illuminated by representative night-sky conditions (e.g., full moon, starlight). Results show that as expected, the precipitous decline in foveal acuity experienced with decreasing mesopic luminance levels is effectively shifted to much lower light levels by use of an image intensification system. The benefits of intensification are most pronounced foveally, but still observable at 20 deg eccentricity. Binocularity provides a small improvement in visual acuity under both intensified and unintensified conditions.

Bradley, Arthur↗
NASA NTRS2007

Dual-Photoelastic-Modulator-Based Polarimetric Imaging Concept for Aerosol Remote Sensing

A dual-photoelastic-modulator- (PEM-) based spectropolarimetric camera concept is presented as an approach for global aerosol monitoring from space. The most challenging performance objective is to measure degree of linear polarization (DOLP) with an uncertainty of less than 0.5% in multiple spectral bands, at moderately high spatial resolution, over a wide field of view, and for the duration of a multiyear mission. To achieve this, the tandem PEMs are operated as an electro-optic circular retardance modulator within a high-performance reflective imaging system. Operating the PEMs at slightly different resonant frequencies generates a beat signal that modulates the polarized component of the incident light at a much lower heterodyne frequency. The Stokes parameter ratio q = Q/I is obtained from measurements acquired from each pixel during a single frame, providing insensitivity to pixel responsivity drift and minimizing polarization artifacts that conventionally arise when this quantity is derived from differences in the signals from separate detectors. Similarly, u = U/I is obtained from a different pixel; q and u are then combined to form the DOLP. A detailed accuracy and tolerance analysis for this polarimeter is presented.

spectropolarimetric imaging↗
NASA NTRS2004

Liquid Crystal on Silicon Wavefront Corrector

A low cost, high resolution, liquid crystal on silicon, spatial light modulator has been developed for the correction of huge aberrations in an optical system where the polarization dependence and the chromatic nature are tolerated. However, the overall system performance suggests that this device is also suitable for real time correction of aberration in human eyes. This device has a resolution of 1024 x 768, and is driven by an XGA display driver. The effective stroke length of the device is 700 nm and 2000 nm for the visible and IR regions of the device, respectively. The response speeds are 50 Hz and 5 Hz, respectively, which are fast enough for real time adaptive optics for aberrations in human eyes. By modulating a wavefront of 2 pi, this device can correct for arbitrary high order wavefront aberrations since the 2-D pixel array is independently controlled by the driver. The high resolution and high accuracy of the device allow for diffraction limited correction of the tip and tilt or defocus without an additional correction loop. We have shown that for every wave of aberration, an 8 step blazed grating is required to achieve high diffraction efficiency around 80%. In light of this, up to 125 waves peak to valley of tip and tilt can be corrected if we choose the simplest aberration. Corrections of 34 waves of aberration, including high order Zernicke terms in a high magnification telescope, to diffraction limited performance (residual wavefront aberration less than 1/30 lambda at 632.8 nm) have been observed at high efficiency.

Pouch, John↗
NASA NTRS1979

Computer Program for Assessing the Economic Feasibility of Solar Energy for Single Family Residences and Light Commercial Applications

Computer program, SHCOST, was used to perform economic analyses of operational test sites. The program allows consideration of the economic parameters which are important to the solar system user. A life cycle cost and cash flow comparison is made between a solar heating system and a conventional system. The program assists in sizing the solar heating system. A sensitivity study and plot capability allow the user to select the most cost effective system configuration.

Forney, J. A.↗
NASA NTRS1988

Optoelectronic techniques for broadband switching

Optoelectronic switching employs a hybrid optical/electronic principle to perform the switching function and is applicable for either analog broadband or high-bit rate digital switching. The major advantages of optoelectronic switching include high isolation, low crosstalk, small physical size, light weight, and low power consumption. These advantages make optoelectronic switching an excellent candidate for on-board satellite switching. This paper describes a number of optoelectronic switching architectures. System components required for implementing these switching architectures are discussed. Performance of these architectures are evaluated by calculating their crosstalk, isolation, insertion loss, matrix size, drive power, throughput, and switching speed. Technologies needed for monolithic optoelectronic switching are also identified.

Su, S. F.↗
NASA NTRS1968

System measures response time of photomultiplier tubes

Calibration system enables precise determination of rise time of photosensitive detectors. To perform a calibration, the time-voltage curve of the excitation voltage for a light source is compared with the time-voltage curve of the voltage output from a photosensitive detector which is responding to the light.

Lauver, M. R.↗