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On the development of a multi-algorithm radar data quality control system at the Naval Research Laboratory
October 24, 2005
Conference Paper
Published in:
32nd Conf. on Radar Meteorology, 24-29 October 2005.
Summary
A radar data quality control (QC) system is being developed for the real-time, continuously updateable NOWCAST system at the Naval Research Laboratory (NRL-NOWCAST) in Monterey, California. NRL has developed its own new radar QC algorithms, and is also working with the MIT Lincoln Laboratory (MIT LL), the National Center for Atmospheric Research (NCAR), the National Severe Storms Laboratory and the Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma (NSSL-OU) to obtain, adapt, integrate, test and install various types of recently-developed radar QC algorithms for use with NRL-NOWCAST. These algorithms work with volume scans of full-resolution Doppler radar data. Radar data QC can be divided into two categories: echo classification (EC) and calibration. New EC algorithms have recently demonstrated substantial success at separating the radar echoes of precipitation from other echo types, such as noise, normal propagation (NP) and anomalous propagation (AP) ground clutter, sea clutter, insects/clear-air, birds, second-trip echoes, and constant power function (CPF) artifacts. Radar data calibration methods assess the accuracy of both the data values and data coordinates. One calibration issue is aliased radial velocity data from precipitation and insect/clear-air returns, which if correctly de-aliased, afford the opportunity to estimate winds. Another calibration issue of concern to NRL is the processing of radar data from mobile platforms, such as US Navy ships. This processing requires corrections to the radial velocity data and the data-coordinates for the motion of the platform, as well as corrections for the altitude of the data coordinates due to the AP of the radar beam that frequently occurs within surface and evaporation ducts of the marine atmosphere. The goal of this work is to test the performance of the most current and promising radar data QC algorithms on archived data sets, both from ground- and sea-based radars, in order to determine the optimal combination for future real-time use within NRL-NOWCAST. NRL-NOWCAST currently ingests full-resolution Doppler radar data from both the Weather Surveillance Radar-1988 Doppler (WSR-88D) network and the US Department of Defense (DoD) Supplemental Weather Radar (SWR) at the Naval Air Station (NAS) in Fallon, NV. Various products are then created from these data for NRL-NOWCAST display. The radar data are also ingested into the COAMPS-0S (R) (Geiszler et al. 2004) data assimilation system at NRL. Figure 1 shows a flow chart that summarizes the processing stages and uses of radar data at NRL. Figure 2 shows an example of the NRL-NOWCAST demonstration site currently set up at Fallon, where the specific products displayed are only a few from a large list that may be chosen by the forecasters at the NAS. This paper presents a brief overview of the concepts behind the various EC and radial velocity de-aliasing algorithms under consideration. Test results from an NRL algorithm-testing platform will also be presented along with some previously published test results from the authors. Additional test results from the platform will be presented at the conference. Methods to address data-value and data coordinate calibration problems associated with Doppler radars onboard US Navy ships are currently being studied; a discussion on future work in this area will be outlined.
Summary
A radar data quality control (QC) system is being developed for the real-time, continuously updateable NOWCAST system at the Naval Research Laboratory (NRL-NOWCAST) in Monterey, California. NRL has developed its own new radar QC algorithms, and is also working with the MIT Lincoln Laboratory (MIT LL), the National Center for...
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Multi-PRI signal processing for the Terminal Doppler Weather Radar, part II: range-velocity ambiguity mitigation
October 1, 2005
Journal Article
Published in:
J. Atmos. Ocean. Technol., Vol. 22, No. 10, October 2005, pp. 1507-1519.
Summary
Multiple pulse-repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to combat range-velocity (RV) ambiguity for the Terminal Doppler Weather Radar (TDWR). In Part I of this two-part paper, an adaptive clutter filtering procedure that yields low biases in the moments estimates was presented. In this part, algorithms for simultaneously providing range-overlay protection and velocity dealiasing using multi-PRI signal transmission and processing are presented. The effectiveness of the multi-PRI RV ambiguity mitigation scheme is demonstrated using simulated and real weather radar data, with excellent results. Combined with the adaptive clutter filter, this technique will be used within the larger context of an adaptive signal transmission and processing scheme in which phase-code processing will be a complementary alternative.
Summary
Multiple pulse-repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to combat range-velocity (RV) ambiguity for the Terminal Doppler Weather Radar (TDWR). In Part I of this two-part paper, an adaptive clutter filtering procedure that yields low biases in the moments estimates was...
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Design considerations for space-based radar phased arrays
June 12, 2005
Conference Paper
Published in:
2005 IEEE MTT-S Int. Microwave Symp. Digest, 12-17 June 2005, pp. 1631-1634.
Summary
Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose challenging requirements on the antenna array, including wide-angle electronic scanning, wide instantaneous bandwidth, large poweraperture product, low sidelobe radiation patterns, lightweight deployable structures, multiple array phase centers, and adaptive pattern synthesis. This paper will discuss key enabling technologies for low earth orbit (LEO) SBR arrays including high efficiency transmit/receive modules and multilayer tile architectures, and the parametric influence of array design variables on the SBR system.
Summary
Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose...
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Multi-PRI signal processing for the terminal Doppler weather radar, part I: clutter filtering
May 1, 2005
Journal Article
Published in:
J. Atmos. Ocean. Technol., Vol. 22, May 2005, pp. 575-582.
Topic:
R&D area:
Summary
Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse response clutter filter designs for multi-PRI signals with excellent magnitude and phase responses. These filters provide strong suppression for use on low-elevation scans and yield low biases of velocity estimates so that accurate velocity dealiasing is possible. Specifically, the filters are designed for use in the Terminal Doppler Weather Radar (TDWR) and are shown to meet base data bias requirements equivalent to the Federal Aviation Administration's specifications for the current TDWR clutter filters. Also an adaptive filter selection algorithm is proposed that bases its decision on clutter power estimated during an initial long-PRI surveillance scan. Simulations show that this adaptive algorithm yields satisfactory biases for reflectivity, velocity, and spectral width. Implementation of such a scheme would enable automatic elimination of anomalous propagation signals and constant adjustment to evolving ground clutter conditions, an improvement over the current TDWR clutter filtering system.
Summary
Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse...
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Design considerations and results for an overlapped subarray radar antenna
March 5, 2005
Conference Paper
Published in:
2005 IEEE Aerospace Conf., 5-12 March 2005, pp. 1087-1092.
Summary
Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of an overlapped subarray antenna includes many signal crossovers and a wide variation in splitting/combining ratios, which make it difficult to maintain required error tolerances. This paper presents the design considerations and results for an overlapped subarray radar antenna, including a custom subarray weighting function and the corresponding circuit design and fabrication. Measured pattern results will be shown for a prototype design compared with desired patterns.
Summary
Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of...
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MIMO radar theory and experimental results
November 7, 2004
Conference Paper
Published in:
38th Asilomar Conf. on Signals, Systems and Computers, Vol. 2, 7-10 November 2004, pp. 300-304.
Topic:
Summary
The continuing progress of Moore's law has enabled the development of radar systems that simultaneously transmit and receive multiple coded waveforms from multiple phase centers and to process them in ways that have been unavailable in the past. The signals available for processing from these Multiple-Input Multiple-Output (MIMO) radar systems appear as spatial samples corresponding to the convolution of the transmit and receive aperture phase centers. The samples provide the ability to excite and measure the channel that consists of the transmit/receive propagation paths, the target and incidental scattering or clutter. These signals may be processed and combined to form an adaptive coherent transmit beam, or to search an extended area with high resolution in a single dwell. Adaptively combining the received data provides the effect of adaptively controlling the transmit beamshape and the spatial extent provides improved track-while-scan accuracy. This paper describes the theory behind the improved surveillance radar performance and illustrates this with measurements from experimental MIMO radars.
Summary
The continuing progress of Moore's law has enabled the development of radar systems that simultaneously transmit and receive multiple coded waveforms from multiple phase centers and to process them in ways that have been unavailable in the past. The signals available for processing from these Multiple-Input Multiple-Output (MIMO) radar systems...
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Wideband aperture coherence processing for next generation radar (NexGen)
July 30, 2004
Project Report
Published in:
MIT Lincoln Laboratory Report NG-3
Topic:
Summary
This report develops robust signal processing architectures and algorithms specifically designed to achieve multi-aperture coherence on transmit and receive. A key feature of our approach is the use of orthogonal radar waveforms that allow the monostatic and bistatic target returns to be separated at each receiver's matched filter output. By analyzing these returns, we may determine the appropriate transmit times and phases in order to cohere the various radar apertures using both narrowband and wideband waveforms. This process increases the array gain on receive to N2 instead of N for the single transmitter case. Furthermore, when hll coherence on transmit is achieved, the array gain is N3. The performance of our coherence algorithms is quantified using Monte Carlo simulations and compared to the Cramer-Rao lower bound. A computational complexity study shows that our aperture coherence algorithms are suitable for a realtime implementation on an SGI Origin 3000 multi-processor computer.
Summary
This report develops robust signal processing architectures and algorithms specifically designed to achieve multi-aperture coherence on transmit and receive. A key feature of our approach is the use of orthogonal radar waveforms that allow the monostatic and bistatic target returns to be separated at each receiver's matched filter output. By...
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Power-law scattering models and nonlinear parametric estimation for super-resolution radar
April 26, 2004
Technical Report
Published in:
MIT Lincoln Laboratory Report TR-1095
Topic:
R&D group:
Summary
This paper introduces a direct solution of the frequency-dependent, GTD-based, scatterer-model parameters leading towards a new modern spectral-estimation technique to be used for enhanced, super-resolution radar analysis. The overcomplete nature of the full GTD scatterer-model basis (positive and negative half-integer power laws) is recognized and overcome by introducing the vector-channel method, well known from communication theory. This physically motivated discretemodel- based analysis eliminates the need for computationally intensive and potentially nonconvergent local optimization procedures. Each scatterer is assigned a half-integer power law that identifies its cross-section frequency dependence and hence restricts the possible underlying physical feature geometries. This analysis opens the possibility for vector-attribute-based feature processing for target recognition that offers the potential for significant improvement in target identification performance.
Summary
This paper introduces a direct solution of the frequency-dependent, GTD-based, scatterer-model parameters leading towards a new modern spectral-estimation technique to be used for enhanced, super-resolution radar analysis. The overcomplete nature of the full GTD scatterer-model basis (positive and negative half-integer power laws) is recognized and overcome by introducing the vector-channel...
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Range-velocity ambiguity mitigation schemes for the enhanced Terminal Doppler Weather Radar
August 6, 2003
Conference Paper
Published in:
37th Int. Conf. on Radar Meteorology, 6-12 August 2003.
Summary
The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA is under development that will provide a modern, open-systems hardware platform and standards-compliant software. The new platform also provides an opportunity to insert algorithms to improve the quality of existing base data products, as well as support future enhancements to the aviation weather services provided by TDWR. There are several outstanding data quality issues with the TDWR. In this paper, we focus on mitigation schemes for the range-velocity ambiguity problem that is especially severe for C-band weather radars such as the TDWR.
Summary
The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA is under development that will provide a modern, open-systems hardware platform and standards-compliant software. The new platform also...
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Observations of non-traditional wind shear events at the Dallas/Fort Worth International Airport
February 28, 2003
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-308
Topic:
R&D area:
Summary
During the past 20 years there has been great success in understanding and detecting microbursts. These "traditional" wind shear events are most prominent in the summer and are characterized by a two-dimensional, divergent outflow associated with precipitation loading from a thunderstorm downdraft or evaporative cooling from high-based rain clouds. Analysis of wind shear loss alerts at the Dallas/Fort Worth International Airport (DFW) from August 1999 through July 2002 reveals that a significant number of the wind shear events were generated by "non-traditional" mechanisms. The "non-traditional" wind shear mechanisms, linear divergence, divergence behind gust fronts, and gravity waves, accounted for one half of the alert events in the period studied. Radar-based algorithms have shown considerable skill in detecting wind shear events. However, the algorithms were developed to identifl features common to the "traditional" events. If the algorithms were modified to detect "non-traditional" wind shear, the corresponding increase in false detections could be unacceptable. Therefore, in this report a new radar-based algorithm is proposed that detects linear divergence, divergence behind gust fronts, and gravity waves for output on the Integrated Terminal Weather System by identifying the radar signatures that are common to these features.
Summary
During the past 20 years there has been great success in understanding and detecting microbursts. These "traditional" wind shear events are most prominent in the summer and are characterized by a two-dimensional, divergent outflow associated with precipitation loading from a thunderstorm downdraft or evaporative cooling from high-based rain clouds. Analysis...
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