Publications
Radar images of Logan Airport and application in automated aircraft tracking
April 4, 1994
Conference Paper
Published in:
SPIE, Vol. 2220, Sensing, Imaging, and Vision for Control and Guidance of Aerospace Vehicles, 4-5 April 1994, pp. 316-327.
Summary
To enhance safety and expedite aircraft traffic control at airports, the Federal Aviation Administration (FAA) is in the process of developing automation aids for controllers and pilots. These automation improvements depend on reliable surveillance of the airport traffic, in the form of computerized target reports for all aircraft. One means of surveillance of the airport is primary radar. A short range radar of this type is called airport surface detection equipment or (ASDE). Lincoln Laboratory is participating in this development program by testing a system of surveillance and automation aids at Logan International Airport in Boston, Mass. This work is sponsored by the FAA. This paper describes the radar equipment being used for surface surveillance at Logan Airport and the characteristics of the radar images it produces. Techniques for automatic tracking of this radar data are also described along with a summary of the tracking performance that has been achieved. Two companion papers in this session relate to this same radar surveillance and provide more in-depth descriptions of the radar processing.
Summary
To enhance safety and expedite aircraft traffic control at airports, the Federal Aviation Administration (FAA) is in the process of developing automation aids for controllers and pilots. These automation improvements depend on reliable surveillance of the airport traffic, in the form of computerized target reports for all aircraft. One means...
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Target detection using radar images of an airport surface
April 4, 1994
Conference Paper
Published in:
SPIE, Vol. 2220, Sensing, Imaging, and Vision for Control and Guidance of Aerospace Vehicles, 4-5 April 1994, pp. 338-356.
Summary
Automation aids which increase the efficiency of the controller and enhance safety are being sought by the Federal Aviation Administration (FAA). This paper describes the target detection algorithms developed by the MIT Lincoln Laboratory as part of the airport surface traffic automation (ASTA) and runway surface safety light system (RSLS) programs sponsored by the FAA that were demonstrated at Logan International Airport in Boston, Mass. from September 1992 through December 1993. A companion paper to this conference describes the ASTA and RSLS system demonstration. Another companion paper describes the tracking algorithms. Real-time, parallel processing implementations of these surveillance algorithms are written in C++ on a Silicon Graphics Inc. Unix multiprocessor. The heavy reliance on commercial hardware, standard operating systems, object oriented design, and high-level computer languages allows a rapid transition from a research environment to a production environment.
Summary
Automation aids which increase the efficiency of the controller and enhance safety are being sought by the Federal Aviation Administration (FAA). This paper describes the target detection algorithms developed by the MIT Lincoln Laboratory as part of the airport surface traffic automation (ASTA) and runway surface safety light system (RSLS)...
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Integrated models of signal and background with application to speaker identification in noise
April 1, 1994
Journal Article
Published in:
IEEE Trans. Speech Audio Process., Vol. 2, No. 2, April 1994, pp. 245-257.
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Summary
This paper is concerned with the problem of robust parametric model estimation and classification in noisy acoustic environments. Characterization and modeling of the external noise sources in these environments is in itself an important issue in noise compensation. The techniques described here provide a mechanism for integrating parametric models of acoustic background with the signal model so that noise compensation is tightly coupled with signal model training and classification. Prior information about the acoustic background process is provided using a maximum likelihood parameter estimation procedure that integrates an a priori model of acoustic background with the signal model. An experimental study is presented in the paper on the application of this approach to text-independent speaker identification in noisy acoustic environments. Considerable improvement in speaker classification performance was obtained for classifying unlabeled sections of conversational speech utterances from a 16-speaker population under cross-environment training and testing conditions.
Summary
This paper is concerned with the problem of robust parametric model estimation and classification in noisy acoustic environments. Characterization and modeling of the external noise sources in these environments is in itself an important issue in noise compensation. The techniques described here provide a mechanism for integrating parametric models of...
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Low altitude wind shear detection using airport surveillance radars
March 29, 1994
Conference Paper
Published in:
Proc. 1994 IEEE Natl. Radar Conf., 29-31 March 1994, pp. 52-57.
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Summary
This paper describes an enhanced weather processor for the Federal Aviation Administration's Airport Surveillance Radar (ASR-9) that will include Doppler wind estimation for the detection of low altitude wind shear, scan-to-scan tracking to provide estimates of the speed and direction of storm movement and suppression' of spurious weather reports currently generated by the ASR-9's six-level weather channel during episodes of anomalous radar energy propagation (AP). This ASR-9 Wind Shear Processor (WSP) will be implemented as a retrofit to the ASR-9 through the addition of interfaces, receiving chain hardware and high-speed digital processing and display equipment. Thunderstorm activity in terminal airspace (the volume extending approximately 30 nmi from an airport and to 15,000 feet altitude) is an obvious safety issue and makes a significant overall contribution to delay in the United States commercial aviation industry. Analysis and on-line testing of the prototype ASR-9 WSP has confirmed that the system can provide operationally beneficial detection of low-altitude wind shear phenomena and enhanced weather situational awareness for Air Traffic Control teams.
Summary
This paper describes an enhanced weather processor for the Federal Aviation Administration's Airport Surveillance Radar (ASR-9) that will include Doppler wind estimation for the detection of low altitude wind shear, scan-to-scan tracking to provide estimates of the speed and direction of storm movement and suppression' of spurious weather reports currently...
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Variable-PRI processing for meteorologic Doppler radars
March 29, 1994
Conference Paper
Published in:
1994 IEEE Natl. Radar Conf., 29-31 March 1994, pp. 85-90.
Summary
In this communication we described how, with nonuniform sampling, the concept of bandlimited extrapolation can be used to obtain unambiguous Doppler velocity estimates in the supra-Nyquist region. The proposed method coherently processes a multi-PRI sample using a generalized form of periodogram analysis. The work is described in the context of meteorologic Doppler processing and includes a discussion of effective suppression for stationary ground clutter when multi-PRI schemes are used.
Summary
In this communication we described how, with nonuniform sampling, the concept of bandlimited extrapolation can be used to obtain unambiguous Doppler velocity estimates in the supra-Nyquist region. The proposed method coherently processes a multi-PRI sample using a generalized form of periodogram analysis. The work is described in the context of...
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Extrapolating storm location using the Integrated Terminal Weather System (ITWS) storm motion algorithm
March 29, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-208
Summary
Storm Motion (SM) is a planned Initial Operational Capability (IOC) algorithm of the FAA's Integrated Terminal Weather System (ITWS). As currently designed, this algorithm will track the movement of storms/cells and convey this tracking information to the ITWS user by means of a graphic display of vectors (for direction) with accompanying numeric reports of storm speed, rounded to the nearest 5 nmi/hr increment. Recognizing that there are occasions when ITWS users could benefit from a more extended product format, Storm Extrapolated Position (SEP) was conceived to supplement the SM product and thereby increase the latter's accessibility as a planning aid. This communication describes a prototype SEP design along with an analysis of its accuracy and observed performance during 1993 ITWS demnstrations in Orlando (FL) and Dallas (TX).
Summary
Storm Motion (SM) is a planned Initial Operational Capability (IOC) algorithm of the FAA's Integrated Terminal Weather System (ITWS). As currently designed, this algorithm will track the movement of storms/cells and convey this tracking information to the ITWS user by means of a graphic display of vectors (for direction) with...
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The polygon-ellipse method of data compression of weather maps
March 28, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-213
Summary
Providing an accurate picture of the weather conditions in the pilot's area of interest could be a highly useful application for ground-to-air data links. The problem with using data links to transmit weather pictures is the large number of bits required to exactly specify a weather image. To make transmission of weather maps practical, a means must be found to compress this image. The Polygon-Ellipse (PE) encoding algorithm developed in this report represents weather regions as ellipses, polygons, and exact patterns. The actual ellipse and polygon parameters are encoded and transmitted; the decoder algorithm redraws the shape from their encoded parameter values and fills in the included weather pixels. Special coding techniques are used in PE to compress the encoding of the shape parameters to achieve further overall compression. The PE algorithm contains procedures for gracefully degrading the fidelity of the transmitted image when necessary to meet a specified bit limit. Pictorial examples of the operation of this algorithm on both Terminal Doppler Weather Radar (TDWR) and ASR-9 radar-generated weather images are presented.
Summary
Providing an accurate picture of the weather conditions in the pilot's area of interest could be a highly useful application for ground-to-air data links. The problem with using data links to transmit weather pictures is the large number of bits required to exactly specify a weather image. To make transmission...
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Terminal Weather Message Demonstration at Orlando, FL, Summer 1993
March 4, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-210
Summary
A successful demonstration of providing a text-based message via VHF data link (ACARS) was carried out at Orlando, FL during the summer of 1993. Five airlines participated in the three-month demonstration, which included an average of 145 Terminal Weather message requests per day. During a heavily-impacted weather day, a total of 220 Terminal Weather requests were made. The format of the Terminal Weather message was developed by an ad hoc committee of pilots, dispatchers, controllers and researchers. The format required a balance between the need for including important information and the need to fit the information into a limited number of characters. The approach was to divide the message into several blocks and to prioritize the potential message elements by importance and immediacy. The most important and timely elements are listed first, and the others appear only if more important elements are not present or else were deleted altogether. Pilot reaction to the demonstration was assessed from questionnaire responses. Overall, pilots thought that the system should be deployed operationally and found that it increased situational awareness. They felt that it provided some help in decision making and did not adversely affect cockpit workload. They also strongly endorsed the need for a graphical version of the Terminal Weather service. Controllers were initially concerned that the data link demonstration would result in increased radio traffic and concomitant controller workload. Prior to the demonstration, changes were made in the Terminal Weather message format to help allay these concerns. Consequently, controllers were surprosed to find that requests for weather information actually decreases over what they normally would expect during a period of heavy weather impact. Thus, evidence was obtained that delivery of Terminal Weather information by data link could decrease controller workload. Dispatchers took a strong and unanticipated interest in the Terminal Weather message. The dispatchers for one airline used the Terminal Weather message to monitor weather conditions at Orlando during a period of heavy weather impact. Special messages also were sent to dispatchers to alert them when wind shear or microburst hazards initially impacted the Orlando airport. Additional demonstration of the Terminal Weather message service are planned for the summer of 1994 at Memphis, TN and Orlando, FL. Results of hte summer 1993 demonstration are being used to make improvements to the message content. A demonstration of a grpahical version of the Terminal Weather message is also planned.
Summary
A successful demonstration of providing a text-based message via VHF data link (ACARS) was carried out at Orlando, FL during the summer of 1993. Five airlines participated in the three-month demonstration, which included an average of 145 Terminal Weather message requests per day. During a heavily-impacted weather day, a total...
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Digital signal processing applications in cochlear-implant research
March 1, 1994
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 7, No. 1, Spring 1994, pp. 31-62.
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Summary
We have developed a facility that enables scientists to investigate a wide range of sound-processing schemes for human subjects with cochlear implants. This digital signal processing (DSP) facility-named the Programmable Interactive System for Cochlear Implant Electrode Stimulation (PISCES)-was designed, built, and tested at Lincoln Laboratory and then installed at the Cochlear Implant Research Laboratory (CIRL) of the Massachusetts Eye and Ear Infirmary (MEEI). New stimulator algorithms that we designed and ran on PISCES have resulted in speech-reception improvements for implant subjects relative to commercial implant stimulators. These improvements were obtained as a result of interactive algorithm adjustment in the clinic, thus demonstrating the importance of a flexible signal-processing facility. Research has continued in the development of a laboratory-based, sohare-controlled, real-time, speech processing system; the exploration of new sound-processing algorithms for improved electrode stimulation; and the design of wearable stimulators that will allow subjects full-time use of stimulator algorithms developed and tested in a laboratory setting.
Summary
We have developed a facility that enables scientists to investigate a wide range of sound-processing schemes for human subjects with cochlear implants. This digital signal processing (DSP) facility-named the Programmable Interactive System for Cochlear Implant Electrode Stimulation (PISCES)-was designed, built, and tested at Lincoln Laboratory and then installed at the...
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Assessment of the weather detection capability of an Airport Surveillance Radar with solid-state transmitter
February 24, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-209
Summary
The Federal Aviation Administration may acquire a new Airport Surveillance Radar-ASR-11-to replace aging ASR-7s and ASR-8s with a digital terminal radar consistent with Advanced Automation System requirements. A survey of the radar manufacturing industry suggests that a solid-state transmitter will likely be a component of this radar. The ASR-11 will feature a digital weather processing channel to measure and display six calibrated levels of precipitation reflectivity. An additional weather surveillance goal is the capability to support detection of low altitude wind shear phenomena. Use of a low peak power, solid-state transmitter and associated pulse compression technology raises several issues with respect to the capability of ASR-11 to meet these weather measurement objectives: 1. ASR-11 sensitivity will be degraded by approximately 16 to 20 dB relative to the Klystron-based ASR-9 at short range. This results because it is not feasible to use pulse compression waveforms to compensate for low peak transmitter power at short range; 2. Stability of a solid state ASR-11 transmitter may significantly exceed that of previous vacuum tube ASR transmitters. Increased clutter suppression capability associated with this enhanced stability could partially offset the reduced sensitivity of ASR-11 in meeting weather detection goals; 3. Pulse compression range sidelobes may resilt in "ghost" images of actual weather features, displaced in range by as much as 10 km. In some circumstances, these could result in false indications of operationally significant weather features such as thunderstorm-induced gust fronts. We examine these issues through straightforward analyses and simulation. Our assessment depends heavily on Doppler weather radar measurements of thunderstorms and associated wind shear phenomena obtained with Lincoln Laboratory's Terminal Doppler Weather Radar and ASR-9 testbeds. Overall, our assessment indicates that a solid-state transmitter ASR-11 can provide six-level weather reflectivity data with accuracy comparable to that of the ASR-9. Detection of low altitude wind shear phenomena using a solid-state transmitter ASR is more problematic. Reduced sensitivity at short range--the range interval of primary operational concern for an on-airport ASR--results in significant degradation of its capability to measure the reflectivity and Doppler velocity signatures associated with gust fronts and "dry" microbursts. This degradation is not offset by the enhanced clutter suppression capability provided by a solid-state transmitter. Although pulse compression range sidelobes do not appear to be a major issue if they are held to the -55 dB level, simulations are presented where range sidelobes result in a false gust front wind shear signature.
Summary
The Federal Aviation Administration may acquire a new Airport Surveillance Radar-ASR-11-to replace aging ASR-7s and ASR-8s with a digital terminal radar consistent with Advanced Automation System requirements. A survey of the radar manufacturing industry suggests that a solid-state transmitter will likely be a component of this radar. The ASR-11 will...
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