Publications
Supporting the deployment of the Terminal Doppler Weather Radar (TDWR)
September 1, 1994
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 7, No. 2, Fall 1994, pp. 379-398.
Summary
The Terminal Doppler Weather Radar (TDWR) program was initiated in the mid-1 980s to develop a reliable automated Doppler-radar-based system for detecting weather hazards in the airport terminal area and for providing warnings that will help pilots avoid these hazards when landing and departing. This article describes refinements made to the TDWR system since 1988, based on subsequent Lincoln Laboratory testing in Kansas City, Missouri, and Orlando, Florida. During that time, Lincoln Laboratory developed new capabilities for the system such as the integration of warnings from TDWR and the Low Level Wind Shear Alert System (LLWAS). Extensive testing with the Lincoln Laboratory TDWR testbed system has reconfirmed the safety benefits of TDWR.
Summary
The Terminal Doppler Weather Radar (TDWR) program was initiated in the mid-1 980s to develop a reliable automated Doppler-radar-based system for detecting weather hazards in the airport terminal area and for providing warnings that will help pilots avoid these hazards when landing and departing. This article describes refinements made to...
READ MORE
The Integrated Terminal Weather System (ITWS)
September 1, 1994
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 7, No. 2, Fall 1994, pp. 449-474.
Summary
The Integrated Terminal Weather System (ITWS) is one of two major development projects sponsored by the FMs Aviation Weather Development Program. Focused on the environment within the airport terminal area, ITWS integrates data from FAA and National Weather Service (NWS) sensors and systems to provide a suite of weather informational products for improving air terminal planning, capacity, and safety. This article provides an overview of the ITWS project, presenting the system concept, some of the design and engineering challenges, and plans for development that will lead to operational systems in the field.
Summary
The Integrated Terminal Weather System (ITWS) is one of two major development projects sponsored by the FMs Aviation Weather Development Program. Focused on the environment within the airport terminal area, ITWS integrates data from FAA and National Weather Service (NWS) sensors and systems to provide a suite of weather informational...
READ MORE
Implementation of the 1992 Terminal Area-Local Analysis and Prediction System (T-LAPS)
August 22, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-219
Summary
The Integrated Terminal Weather System (ITWS) development program was initiated by the Federal Aviation Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service (NWS) sensors as well as from aircraft in flight in the terminal area. The ITWS will provide air traffic personnel with products that are immediately usable without further metorological interpretation. These products include current terminal area weather and short-term (0-30 minute) predictions of significant weather phenomena. The Terminal area-Local Analysis and Prediction System (T-LAPS) is being evaluated as a possible provider of the Terminal Winds Product for the ITWS. T-LAPS is a direct descendant of the Local Analysis and Prediction System (LAPS) developed at the National Oceanic and Atmospheric Administraiton's (NOAA's) Forecast Systems Laboratory (FSL). T-LAPS takes meteorological data from a wide variety of data sources as input and provides a gridded, three-dimensional (3-D) analysis of the state of the local atmosphere in the terminal area as output. For the 1992 system, the output was a gridded 3-D analysis of the horizontal winds. This information is intended to be used by the Terminal Air Traffic Control Automation (TATCA) program to estimate the effects of winds on aircraft in the terminal area. The 1993 and 1994 T-LAPS systems will incorporate more sophisticated wind analysis algorithms. The T-LAPS '92 demonstration at the Lincoln Laboratory Terminal Doppler Weather Radar (TDWR) FL-2CC field site in Kissimmee, Florida, during August and September was quite successful. The primary area of coverage was a 120 km by 120 km box centered on the Orlando International Airport. The T-LAPS system was able to utilize radar information from both the TDWR testbed and the operational NEXRAD/WSR-88D radar in Melbourne, Florida. This report documents the implementation of the T-LAPS system that was run during the 1992 summer demonstration and discusses the design and some implementation details of the system.
Summary
The Integrated Terminal Weather System (ITWS) development program was initiated by the Federal Aviation Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service (NWS)...
READ MORE
Large population speaker recognition using wideband and telephone speech
July 28, 1994
Conference Paper
Published in:
Proc. SPIE, Vol. 2277, Automatic Systems for the Identification and Inspection of Humans, 28-29 July 1994, pp. 111-120.
Topic:
R&D area:
Summary
The two largest factors affecting automatic speaker identification performance are the size of the population to be distinguished among and the degradations introduced by noisy communication channels (e.g. telephone transmission). To experimentally examine these two factors, this paper presents text-independent speaker identification results for varying speaker population sizes up to 630 speakers for both clean, wideband speech and telephone speech. A system based on Gaussian mixture speaker models is used for speaker identification and experiments are conducted on the TIMIT and NTIMIT databases. The aims of this study are to (1) establish how well text-independent speaker identification can perform under near ideal conditions for very large populations (using the TIMIT database), (2) gauge the performance loss incurred by transmitting the speech over the telephone network (using the NTIMIT database), and (3) examine the validity of current models of telephone degradations commonly used in developing compensation techniques (using the NTIMIT calibration signals). This is believed to be the first speaker identification experiments on the complete 630 speaker TIMIT and NTIMIT databases and the largest text-independent speaker identification task reported to date. Identification accuracies of 99.5% and 60.7% are achieved on the TIMIT and NTIMIT databases, respectively.
Summary
The two largest factors affecting automatic speaker identification performance are the size of the population to be distinguished among and the degradations introduced by noisy communication channels (e.g. telephone transmission). To experimentally examine these two factors, this paper presents text-independent speaker identification results for varying speaker population sizes up to...
READ MORE
Documentation of 9-PAC Beacon Target Detector processing function
July 26, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-220
Summary
This project report documents the algorithms and flow of the Beacon Target Detector (BTD) processing function incorporated as part of the ASR-9 Processor Augmentation Card (9-PAC). The BTD function combines replies that arise from the same aircraft to form beacon targets, and sends these beacon targets to the 9-PAC merge process where they are combined with primary radar reports. The 9-PAC BTD process was designed to solve two problems with the ASR-9 Array Signal Processor (ASP) BTD: identifying and removing false beacon targets due to reflections, and preventing merging or splitting of targets due to reply overlap and garble. The BTD reflection processing algorithm marks each beacon target as either real or false, and provides this information to the 9-PAC merge process. Discrete Mode A reflection false targets are identified when duplicate code reports satisfying stringent conditions are located. In order to find non-discrete Mode A code reflection false targets, the BTD builds an automated, dynamic reflector database based on the geography of pairs of discrete real and false targets.
Summary
This project report documents the algorithms and flow of the Beacon Target Detector (BTD) processing function incorporated as part of the ASR-9 Processor Augmentation Card (9-PAC). The BTD function combines replies that arise from the same aircraft to form beacon targets, and sends these beacon targets to the 9-PAC merge...
READ MORE
Solid state radar demonstration test results at the FAA technical center
June 17, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-221
Summary
In 1992 and 1993 ITT Gilfillan teamed with Thomson CSF to develop a solid state transmitter system for airport surveillance radar applications. Because of the low peak power limitations of the solid state transmitter, the radar uses pulse compression techniques to obtain 55 nmi detection performance. In the Fall of 1992 ITT/Thompson executed a Cooperative Research and Development Agreement with the FAA?s Terminal Area Surveillance System (TASS) program office to demonstrate the transmitter at the FAA Technical Center using the FAATC's ASR-9. The Laboratory participated in these tests, which were completed in April 1993. The Laboratory test plan included an assessment of the solid state radar's time sidelobe levels, stability, susceptibility to short pulse interference, and target detection performance. Although the tests were limited in scope and the data required several post-collection processing corrections, the radar exhibited very low time sidelobe levels, had excellent stability, and showed adequate detection performance. The pulse compression receiver was vulnerable to short pulse interference and will require specialized processing techniques to minimize its effects. It was not possible to take weather data, and the FAA Technical Center radar environment has no stressing clutter. Recommendations are made for the follow-on effort at a mountainous site to more completely characterize the solid state ATC radar.
Summary
In 1992 and 1993 ITT Gilfillan teamed with Thomson CSF to develop a solid state transmitter system for airport surveillance radar applications. Because of the low peak power limitations of the solid state transmitter, the radar uses pulse compression techniques to obtain 55 nmi detection performance. In the Fall of...
READ MORE
Airport surface surveillance using differential GPS and the Mode S data link
June 6, 1994
Conference Paper
Published in:
Proc. 50th Annual Mtg. of the Institute of Navigation, 6-8 June 1994, pp. 335-344.
Summary
A new concept for providing surface surveillance of aircraft and ground vehicles has recently been tested at Hanscom Field in Bedford, Massachusetts. This concept, known as GPS-Squitter, combines the capabilities of differential GPS for navigation with those of the Mode S data link for communications. Together these systems provide accurate surveillance data along with a positive identification of surface traffic, both very important for an effective surface meillance system. The GPS-Squitter concept is based on the use of the Mode S squitter. The current squitter is a 56bit Mode S all-call reply message spontaneously broadcast by all aircraft Mode S transponders at a 1Hz rate. This message provides the unique Mode S address of an aircrsft and is used by TCAS (Traffic Alert and Collision Avoidance System) for acquisition of nearby aircraft. In the Hanscom testing, this squitter was extended to include GPS-based surveillance information. Two target vehicles participated in the experiments - one aircraft and one ground vehicle. They determined their position, heading, and speed using differential GPS and automatically broadcast that surveillance information to ground transmit/receive stations using the modified squitter. Differential GPS pseudorange and pseudorange rate corrections were formed by a reference station located at Hanscom Field and were transmitted by the ground transmit receive stations to the target vehicles. This paper describes the configuration of the target vehicles, the ground transmit/receive stations, and the differential GPS reference station. Results of the surface surveillance testing are provided including: system coverage, surveillance update rate, and differential GPS data quality. Ongoing testing at Logan International Airport is also discussed.
Summary
A new concept for providing surface surveillance of aircraft and ground vehicles has recently been tested at Hanscom Field in Bedford, Massachusetts. This concept, known as GPS-Squitter, combines the capabilities of differential GPS for navigation with those of the Mode S data link for communications. Together these systems provide accurate...
READ MORE
Demonstration of GPS Automatic Dependent Surveillance of aircraft using spontaneous Mode S broadcast messages
June 1, 1994
Journal Article
Published in:
Navig. J. Inst. Navig., Vol. 41, No. 2, Summer 1994, pp. 187-206.
Topic:
R&D area:
R&D group:
Summary
A new Automatic Dependent Surveillance (ADS) system concept combining GPS-based positions with Mode S data communications is described. Several potential applications of this concept are presented with emphasis on surface surveillance at airports. The navigation and data link performance are analyzed. Compact ADS position formats are included. The results of the first tests at Hanscom Field, demonstrating the feasibility of the spontaneous broadcast of ADS positions using Mode S messages are presented. Test aircraft, vehicles, avionics equipment and the ground system configuration are described. Avionics standards and GPS interface requirements are discussed. Multipath and airport surface coverage issues are addressed. Further testing in an operational environment is continuing at Logan Airport.
Summary
A new Automatic Dependent Surveillance (ADS) system concept combining GPS-based positions with Mode S data communications is described. Several potential applications of this concept are presented with emphasis on surface surveillance at airports. The navigation and data link performance are analyzed. Compact ADS position formats are included. The results of...
READ MORE
ITWS and the NWS forecaster: what is the connection?
June 1, 1994
Journal Article
Published in:
Nat. Weather Dig., Vol. 18, No. 4, June 1994, pp. 43-47.
Summary
The Federal Aviation Administration (FAA) is sponsoring the development of the Integrated Terminal Weather System (ITWS), which is designed to acquire all of the weather data that is available in the terminal area, both ground-based and aircraft sensed, and to provide short-term (0 to 30-minute) predictions of microbursts, wind shear, gust fronts, runway winds and terminal-area ceiling and visibility. Additionally, the ITWS will be generating the 4-dimensional wind field at many levels in the terminal area, mainly for use by other FAA terminal air traffic control automation systems, but also available as a graphical display. An area of interest and concern to the developers is the interaction between the automated, very-short-term predictions of the ITWS, and the National Weather Service (NWS) aviation meteorologist, who is responsible for issuing terminal forecasts and other aviation advisory and warning products. This paper will describe the ITWS as currently planned and will explore the possible relationships between the ITWS and the NWS forecaster. Consideration will also be given to the NWS's new Advanced Weather Interactive Processing System (AWIPS) and how ITWS information might be used in the terminal forecasting process. This paper is intended to spark discussion of the role of the ITWS in the NWS forecasting process of the future.
Summary
The Federal Aviation Administration (FAA) is sponsoring the development of the Integrated Terminal Weather System (ITWS), which is designed to acquire all of the weather data that is available in the terminal area, both ground-based and aircraft sensed, and to provide short-term (0 to 30-minute) predictions of microbursts, wind shear...
READ MORE
An automated method for low level wind shear alert system (LLWAS) data quality analysis
May 26, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-207
Summary
The Low Level Windshear Alert System (LLWAS) is an anemometer-based surface network used for detection of hazardous wind shear and acquisition of operational wind information in the airport terminal area. The quality of wind data provided by the LLWAS anemometers is important for the proper performance of the LLWAS wind shear detection algorithms. This report describes the development of an automated method for anemometer data quality (DQA). This method identifies potential data quality problems through comparison of wind data from each sensor within a network to the mean wind speed and direction of the entire network. The design approach and implementation are described, and results from testing using data from the demonstration Phase III LLWAS network in Orlando, FL are reported. Potential improvements to the automated DQA algorithm are presented based on experience gained during analysis of the Orlando data. These recommended improvements are provided to assist future development and refinement of the DQA methodology to be performed by the FAA Technical Center.
Summary
The Low Level Windshear Alert System (LLWAS) is an anemometer-based surface network used for detection of hazardous wind shear and acquisition of operational wind information in the airport terminal area. The quality of wind data provided by the LLWAS anemometers is important for the proper performance of the LLWAS wind...
READ MORE