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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 91 records · Page 5

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NASA NTRS1992

Acquisition and use of Orlando, Florida and Continental Airbus radar flight test data

Westinghouse is developing a lookdown pulse Doppler radar for production as the sensor and processor of a forward looking hazardous windshear detection and avoidance system. A data collection prototype of that product was ready for flight testing in Orlando to encounter low level windshear in corroboration with the FAA-Terminal Doppler Weather Radar (TDWR). Airborne real-time processing and display of the hazard factor were demonstrated with TDWR facilitated intercepts and penetrations of over 80 microbursts in a three day period, including microbursts with hazard factors in excess of .16 (with 500 ft. PIREP altitude loss) and the hazard factor display at 6 n.mi. of a visually transparent ('dry') microburst with TDWR corroborated outflow reflectivities of +5 dBz. Range gated Doppler spectrum data was recorded for subsequent development and refinement of hazard factor detection and urban clutter rejection algorithms. Following Orlando, the data collection radar was supplemental type certified for in revenue service on a Continental Airlines Airbus in an automatic and non-interferring basis with its ARINC 708 radar to allow Westinghouse to confirm its understanding of commercial aircraft installation, interface realities, and urban airport clutter. A number of software upgrades, all of which were verified at the Receiver-Transmitter-Processor (RTP) hardware bench with Orlando microburst data to produce desired advanced warning hazard factor detection, included some preliminary loads with automatic (sliding window average hazard factor) detection and annunciation recording. The current (14-APR-92) configured software is free from false and/or nuisance alerts (CAUTIONS, WARNINGS, etc.) for all take-off and landing approaches, under 2500 ft. altitude to weight-on-wheels, into all encountered airports, including Newark (NJ), LAX, Denver, Houston, Cleveland, etc. Using the Orlando data collected on hazardous microbursts, Westinghouse has developed a lookdown pulse Doppler radar product with signal and data processing algorithms which detect realistic microburst hazards and has demonstrated those algorithms produce no false alerts (or nuisance alerts) in urban airport ground moving vehicle (GMTI) and/or clutter environments.

Eide, Michael C.↗

NASA NTRS1993

Precipitation measurement using SIR-C: A feasibility study

A precipitation detection and measurement experiment is planned for the SIR-C/X-SAR mission. This study was conducted to determine under what conditions an off-nadir experiment is feasible. The signal-to-clutter ratio, the signal-to-noise ratio, and the minimum detectable rain rate were investigated. Available models, used in previous studies, were used for the surface clutter and the rain echo. The study also considers the attenuation of the returns at X band. It was concluded that an off-nadir rain-measurement experiment is feasible only for rain rates greater than 10 mm/hr for look angles greater than 60 deg. For the range of look angles 5 less than theta(sub 1) less than 50, the rain rate required is very high for adequate signal-to-clutter ratio, and hence the feasibility of the experiment.

Ahamad, Atiq↗

NASA NTRS1994

Effective declutter of complex flight displays using stereoptic 3-D cueing

The application of stereo technology to new, integrated pictorial display formats has been effective in situational awareness enhancements, and stereo has been postulated to be effective for the declutter of complex informational displays. This paper reports a full-factorial workstation experiment performed to verify the potential benefits of stereo cueing for the declutter function in a simulated tracking task. The experimental symbology was designed similar to that of a conventional flight director, although the format was an intentionally confused presentation that resulted in a very cluttered dynamic display. The subject's task was to use a hand controller to keep a tracking symbol, an 'X', on top of a target symbol, another X, which was being randomly driven. In the basic tracking task, both the target symbol and the tracking symbol were presented as red X's. The presence of color coding was used to provide some declutter, thus making the task more reasonable to perform. For this condition, the target symbol was coded red, and the tracking symbol was coded blue. Noise conditions, or additional clutter, were provided by the inclusion of randomly moving, differently colored X symbols. Stereo depth, which was hypothesized to declutter the display, was utilized by placing any noise in a plane in front of the display monitor, the tracking symbol at screen depth, and the target symbol behind the screen. The results from analyzing the performances of eight subjects revealed that the stereo presentation effectively offsets the cluttering effects of both the noise and the absence of color coding. The potential of stereo cueing to declutter complex informational displays has therefore been verified; this ability to declutter is an additional benefit from the application of stereoptic cueing to pictorial flight displays.

Parrish, Russell V.↗

NASA NTRS1994

Motion-sensitive optical correlator using a VanderLugt correlator

A new type of optical correlator is presented. The correlator performs motion detection or background clutter suppression and correlation simultaneously in a single photorefractive crystal. Additionally, the device is useful for moving target identification and tracking and for stationary clutter rejection. The correlation is of the VanderLugt type, and the motion detection or background clutter suppression is based on the erasing property of photorefractive crystals.

Liu, Tsuen-Hsi↗

DOE OSTI2025

Visualization of Noisy and Less Noisy Computational Basis States in Quantum Computing

Quantum computing technology holds substantial promise as a reliable computational paradigm. However, current noisy intermediate scale quantum (NISQ) systems, are significantly impacted by noise originating from hardware inconsistencies. This noise causes errors and lowers output fidelity. So we must find which basis states cause errors. However, there are two main challenges in analyzing noise corresponding to basis states. First, the noise distribution data is high dimensional in nature, thereby making its analysis challenging. Second, although functional box plots have been used in the state of the art research to understand such a high dimensional data, they suffer from clutter and occlusion issues because of overplotting. In this study, we introduce an innovative visualization pipeline to address the aforementioned challenges to provide a clear depiction of noisy and less-noisy basis states. Specifically, our proposed visualization pipeline comprises three stages namely, low dimensional embedding, clustering, and violin plot visualization, to reduce visual clutter and effectively analyze high-dimensional noise distribution data. Our analysis uses quantum machine learning (QML) circuits as case study for drawing a distinction between noisy and less noisy basis states.

Senapati, Priyabrata [Kent State University]↗

DOE OSTI2020

Antenna Requirements for GMTI Radar Systems

A principal performance-enabling, or performance-limiting, component of Ground-Moving-Target-Indication (GMTI) radar systems is the antenna. Undesired clutter leakage into antenna sidelobes can be particularly problematic, generating undesired false alarms. GMTI system antennas can be designed with characteristics and features to allow discriminating and depressing/suppressing problematic sidelobe leakage of clutter and other undesired signals. We offer analysis and design guidelines for doing so.

42 ENGINEERING↗

NASA NTRS1970

Phenomenological approach to scatterometer data interpretation

A graphic method of analyzing radar scatterometer sea clutter data leading to linear relations between scattering cross sections and tan angle of incidence of the radiation is proposed. This relation permits formulation of simple analytic relations without reference to the ocean surface spectrum. Parameters introduced depend on the wavelength of the incident radiation and its polarization, and on wind and sea states. The simplicity of the expressions derived suggests a corresponding simplicity in the physical mechanism of radar sea clutter return.

Alzofon, F. E.↗

NASA NTRS1976

Feasibility of an Incoherent-scatter Radar Aboard the Space Shuttle

The results of a preliminary study to investigate the feasibility of conducting an incoherent scatter radar experiment on board the space shuttle are presented. The results indicate that such an experiment is technically feasible. The more difficult questions to answer are whether the system can be made flexible enough to justify the problems and costs involved. The design parameters and the tradeoffs that are available in the consideration of these questions are evaluated. Some of the more serious limitations pertain to: (1) the presence of ground clutter and F region auroral clutter; (2) available average power; (3) weight and volume associated with required antenna size, transmitter, and energy storage devices; and (4) antenna breakdown associated with high power transmitter problems.

Baron, M. J.↗

NASA NTRS1977

Study to investigate and evaluate means of optimizing the Ku-band combined radar/communication functions for the space shuttle

The performance of the space shuttle orbiter's Ku-Band integrated radar and communications equipment is analyzed for the radar mode of operation. The block diagram of the rendezvous radar subsystem is described. Power budgets for passive target detection are calculated, based on the estimated values of system losses. Requirements for processing of radar signals in the search and track modes are examined. Time multiplexed, single-channel, angle tracking of passive scintillating targets is analyzed. Radar performance in the presence of main lobe ground clutter is considered and candidate techniques for clutter suppression are discussed. Principal system parameter drivers are examined for the case of stationkeeping at ranges comparable to target dimension. Candidate ranging waveforms for short range operation are analyzed and compared. The logarithmic error discriminant utilized for range, range rate and angle tracking is formulated and applied to the quantitative analysis of radar subsystem tracking loops.

Weber, C. L.↗

NASA NTRS1977

The estimation of pointing angle and normalized surface scattering cross section from GEOS-3 radar altimeter measurements

The statistical error of the pointing angle estimation technique is determined as a function of the effective receiver signal to noise ratio. Other sources of error are addressed and evaluated with inadequate calibration being of major concern. The impact of pointing error on the computation of normalized surface scattering cross section (sigma) from radar and the waveform attitude induced altitude bias is considered and quantitative results are presented. Pointing angle and sigma processing algorithms are presented along with some initial data. The intensive mode clean vs. clutter AGC calibration problem is analytically resolved. The use clutter AGC data in the intensive mode is confirmed as the correct calibration set for the sigma computations.

Brown, G. S.↗

NASA NTRS1980

Early flight test experience with Cockpit Displayed Traffic Information (CDTI)

Coded symbology, based on the results of early human factors studies, was displayed on the electronic horizontal situation indicator and flight tested on an advanced research aircraft in order to subject the coded traffic symbology to a realistic flight environment and to assess its value by means of a direct comparison with simple, uncoded traffic symbology. The tests consisted of 28 curved, decelerating approaches, flown by research-pilot flight crews. The traffic scenarios involved both conflict-free and blunder situations. Subjective pilot commentary was obtained through the use of a questionnaire and extensive pilot debriefing sessions. The results of these debriefing sessions group conveniently under either of two categories: display factors or task performance. A major item under the display factor category was the problem of display clutter. The primary contributors to clutter were the use of large map-scale factors, the use of traffic data blocks, and the presentation of more than a few aircraft. In terms of task performance, the cockpit displayed traffic information was found to provide excellent overall situation awareness.

Abbott, T. S.↗

NASA NTRS1980

Flight investigation of cockpit-displayed traffic information utilizing coded symbology in an advanced operational environment

Traffic symbology was encoded to provide additional information concerning the traffic, which was displayed on the pilot's electronic horizontal situation indicators (EHSI). A research airplane representing an advanced operational environment was used to assess the benefit of coded traffic symbology in a realistic work-load environment. Traffic scenarios, involving both conflict-free and conflict situations, were employed. Subjective pilot commentary was obtained through the use of a questionnaire and extensive pilot debriefings. These results grouped conveniently under two categories: display factors and task performance. A major item under the display factor category was the problem of display clutter. The primary contributors to clutter were the use of large map-scale factors, the use of traffic data blocks, and the presentation of more than a few airplanes. In terms of task performance, the cockpit-displayed traffic information was found to provide excellent overall situation awareness. Additionally, mile separation prescribed during these tests.

Abbott, T. S.↗

NASA NTRS1981

A pilot's subjective analysis of a Cockpit Display of Traffic Information (CDTI)

Both the advent of electronic displays for cockpit applications and the availability of high-capacity data transmission systems, linking aicraft with ATC ground computers, offer the opportunity of expanding the pilots' role in the distributive management process. A critical element in this process is believed to be the presentation to the pilot of his traffic situation. A representative cockpit display of traffic information (CDTI) system is presented as viewed from the pilot in the cockpit, and the research results from flight tests presented. The use of advanced controls and displays allows for presentation to the pilot, large quantities of information that he has not had before. The real challenge in the design of an operational CDTI system will be the satisfaction of needs for information and the presentation of all necessary information, only in a useable format in order to avoid clutter. Even though a reasonably large display was utilized in these tests, display clutter was the primary problem from the standpoint of information assimilation.

Keyser, G. L., Jr.↗

NASA NTRS1983

Stratosphere and troposphere (S-T) studies at Millstone Hill. Recent results, capabilities and limitations

The 440-MHz incoherent-scatter radar at Millstone Hill has been used in recent years for studies of the troposphere and lower stratosphere with a fully steerable 150' antenna. The configuration of the radar system is briefly outlined. Clear-air returns are received over an altitude range 4 to 25 km. The power spectra of these returns can be measured with a range resolution of up to 300 m and a Doppler resolution of up to 4 cm/sec. Due to the lack of a natural shield around the radar, the ground clutter at Millstone is more severe than at other installations. With the use of a fine Doppler resolution, however, the atmospheric returns are readily discriminated from the clutter. Observations of turbulence structures, spatial inhomogeneity of turbulence, and enhanced turbulence associated with convective phenomena are described. Capabilities and limitations of the Millstone S-T radar are pointed out.

Rastogi, P. K.↗

NASA NTRS1985

Microwave properties of a quiet sea

The microwave flux responses of a quiet sea are observed at five microwave frequencies and with both horizontal and vertical polarizations at each frequency--a simultaneous 10 channel receiving system. The measurements are taken from Earth orbit with an articulating antenna. The 10 channel responses are taken simultaneously since they share a common articulating collector with a multifrequency feed. The plotted flux responses show: (1) the effects of the relative, on-axis-gain of the collecting aperture for each frequency; (2) the effects of polarization rotation in the output responses of the receive when the collecting aperture mechanically rotates about a feed that is fixed; (3) the difference between the flux magnitudes for the horizontal and vertical channels, at each of the five frequencies, and for each pointing position, over a 44 degree scan angle; and (4) the RMS value of the clutter--as reckoned over the interval of a full swath for each of the 10 channels. The clutter is derived from the standard error of estimate of the plotted swath response for each channel. The expected value of the background temperature is computed for each of the three quiet seas. The background temperature includes contributions from the cosmic background, the downwelling path, the sea surface, and the upwelling path.

Stacey, J.↗

NASA NTRS1985

Experimental radar Doppler wind profile measurements at Kennedy Space Center

A wind profile radar demonstration project was sponsored by the Space Transportation System (STS) Program Office to study the feasibility of incorporating continuous, high time resolution radar wind data into STS operations. This project required wind profile radars to be deployed in the vicinity of the Shuttle launch site into an environment quite unlike typical VHF profiler sites. Two 50 MHz radars were operated at the Kennedy Space Center in environments that were noisy in terms of RFI, large stationary ground clutter sources, non-stationary clutter sources, and heavy local aircraft traffic. Processing compensation for these operational constraints magnified design limitations of the research-level radars used in the demonstration. This report addresses the importance of system design for unique or particular applications with reference to finite radiation patterns, zero-Doppler processing, radar frequency, and beam pointing.

Jost, R. J.↗

NASA NTRS1986

An evaluation of errors observed in the measurement of low wind velocities

Measurements of low wind velocities (the absolute value of V sub H is approx. equal to 6 m/s) with a VHF wind profiler can be difficult if ground clutter or other biases in the system dominate in altering the position of the perceived peak in the calculated power spectrum. A variety of methods for ground clutter suppression are used in profiler systems today (Cornish, 1983). An editing method called zero suppression takes the spectral value of selectable number of points (N) on each side of 0 velocity (one point on either side, in this study) and sets them equal to the mean value of the points exterior to the specified N points on either side of 0. Analysis done with the PSU VHF(1) radar, shows that this zero-suppression method can systematically bias horizontal wings V sub H below 6 m/s. With the zero suppression, an artificial increase in absolute wind velocities occurs when the spectral peaks fall within the plus or minus N points of the FFT (personal communication, Strauch, 1985). It was also established that the method artificially decreases the absolute wind velocities inferred from spectral peaks that are outside but near the suppressed region. Comparisons of wind profiles observed with and without zero suppression are given. The range of the biased velocities extends to about plus or minus 6 m/s. Biases have been deduced to be as much as 2 m/s, but more commonly they are on the order of 1.0 m/s.

Williams, S. R.↗

NASA NTRS1986

Geostationary microwave imagers detection criteria

Geostationary orbit is investigated as a vantage point from which to sense remotely the surface features of the planet and its atmosphere, with microwave sensors. The geometrical relationships associated with geostationary altitude are developed to produce an efficient search pattern for the detection of emitting media and metal objects. Power transfer equations are derived from the roots of first principles and explain the expected values of the signal-to-clutter ratios for the detection of aircraft, ships, and buoys and for the detection of natural features where they are manifested as cold and warm eddies. The transport of microwave power is described for modeled detection where the direction of power flow is explained by the Zeroth and Second Laws of Thermodynamics. Mathematical expressions are derived that elucidate the detectability of natural emitting media and metal objects. Signal-to-clutter ratio comparisons are drawn among detectable objects that show relative detectability with a thermodynamic sensor and with a short-pulse radar.

Stacey, J. M.↗