Publications
ADS-Mode S system overview
October 25, 1993
Conference Paper
Published in:
AIAA/IEEE Digital Avionics Systems Conf., 25-28 October 1993, pp. 104-109.
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Summary
ADS-Mode S is a system concept that merges the capabilities of Automatic Dependent Surveillance and the Mode S beacon radar. The result is an integrated system for seamless surveillance and data link that permits equipped aircraft to participate in ADS or beacon ground environments. This offers many possibilities for transitioning from a beacon to an ADS based surveillance system. The ADS-Mode S squitter. The current Mode S squitter is a spontaneous, periodic (once per second) 56-bit broadcast message containing the Mode S 24-bit address. This broadcast is provided by all Mode S transponders and is used by the Traffic Alert and Collision Avoidance System (TCAS) to acquire nearby Mode S equipped aircraft. For ADS-Mode S use, this squitter broadcast would be extended to 112 bits to provide for the transmission of a 56-bit ADS message field. The ADS squitter would be transmitted in addition to the current TCAS squitter in order to maintain compatibility with current TCAS equipment during transition.
Summary
ADS-Mode S is a system concept that merges the capabilities of Automatic Dependent Surveillance and the Mode S beacon radar. The result is an integrated system for seamless surveillance and data link that permits equipped aircraft to participate in ADS or beacon ground environments. This offers many possibilities for transitioning...
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ADS-Mode S
October 24, 1993
Conference Paper
Published in:
Proc. 38th Annual Air Traffic Control Association Convention, 24-28 October 1993, pp. 230-236.
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Summary
The International Civil Aviation Organization (ICAO) has defined a concept for communications, navigation, and surveillance for the next century known as the Future Air Navigation System (FANS). A cornerstone, of the FANS is an increasing reliance on satellite-based position-determining systems such as the Global Positioning System (GPS). In the case of, surveillance, aircraft position information is automatically downlinked to ground controllers. This technique is known as Automatic Dependent Surveillance (ADS). ADS-Mode S is an ADS system concept utilizing the frequencies and formats of the Mode S system for downlinking position information and also uplinking differential GPS (DGPS) corrections. The result is an integrated concept for surveillance that permits aircraft equipped with a Mode S transponder and a GPS receiver to participate in both ADS and beacon ground environments. This makes possible a smooth transition of the National Airspace System (NAS) secondary surveillance system from a beacon-based to an ADS-based environment. In addition, several other benefits from ADS-Mode S accrue to the Traffic Alert and Collision Avoidance System (TCAS) and to the Mode S Data Link system.
Summary
The International Civil Aviation Organization (ICAO) has defined a concept for communications, navigation, and surveillance for the next century known as the Future Air Navigation System (FANS). A cornerstone, of the FANS is an increasing reliance on satellite-based position-determining systems such as the Global Positioning System (GPS). In the case...
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ASR-9 Microburst Detection Algorithm
October 22, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-197
Summary
The ASR-9 Wind Shear Processor (WSP) is intended as an economical alternative for those airports that have not been slated to receive a Terminal Doppler Weather Radar (TDWR) but have, or will be receiving, an ASR-9 radar. Lincoln Laboratory has developed a prototype ASR-9 WSP system which has been demonstrated during the summer months of the past three year in Orlando, Florida. During the operational test period, microburst and gust front warnings, as well as storm motion indications, were provided to the Air Traffic Control in real time. The ASR-9 Microburst Detection Algorithm (AMDA) is based on the earlier TDWR Microburst Detection Algorithm but has been substantially modified to match better the particular strengths and weaknesses of the ASR-9 rapid-scanning fan-beam radar. The most significant additions included a capability to detect overhead microbursts, a reflectivity processing step used to help detect velocity signatures that have been biased by overhanging precipitation, and a modification to some of the shear segment grouping and thresholding parameters to accommodate better the typical on-air siting of the ASR-9. In addition, the AMDA has been designed to be as efficient as possible to allow it to run at the radar's 4.8 seconds/scan antennas rotation rate on a single-board computer. A detailed description of AMDA, as well as the performance evaluation strategy and results, are presented in this report.
Summary
The ASR-9 Wind Shear Processor (WSP) is intended as an economical alternative for those airports that have not been slated to receive a Terminal Doppler Weather Radar (TDWR) but have, or will be receiving, an ASR-9 radar. Lincoln Laboratory has developed a prototype ASR-9 WSP system which has been demonstrated...
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CW operation of monolithic arrays of surface-emitting AlGaAs diode lasers with dry-etched vertical facets and parabolic deflecting mirrors
October 1, 1993
Journal Article
Published in:
IEEE Photonics Technol. Lett., Vol. 5, No. 10, October 1993, pp. 1146-1149.
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Summary
A monolithic two-dimensional array of surface-emitting AlGaAs diode lasers with dry-etched vertical facets and parabolic deflecting mirrors was mounted junction-side up on a W / Cu microchannel heatsink and evaluated under continuous-wave (CW) operating conditions. Both the facets and parabolic deflecting mirrors were etched using chlorine ion-beam-assistd etching. Threshold current densities of different sections of the array were consistently around 240 A/cm (to the second power), and measured CW differential quantum efficiencies were in the 46-48% range. CW power densities as high as 148 W/cm (to the second power) were achieved with an average temperature rise of less than 25 degrees C in this junction-side-up configuration.
Summary
A monolithic two-dimensional array of surface-emitting AlGaAs diode lasers with dry-etched vertical facets and parabolic deflecting mirrors was mounted junction-side up on a W / Cu microchannel heatsink and evaluated under continuous-wave (CW) operating conditions. Both the facets and parabolic deflecting mirrors were etched using chlorine ion-beam-assistd etching. Threshold current...
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The gust-front detection and wind-shift algorithms for the Terminal Doppler weather radar system
October 1, 1993
Journal Article
Published in:
J. Atmos. Ocean. Technol., Vol. 10, October 1993, pp. 693-709.
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Summary
The Federal Aviation Administration's Terminal Doppler Weather Radar (TDWR) system was primarily designed to address the operational needs of pilots in the avoidance of low-altitude wind shears upon takeoff and landing at airports. One of the primary methods of wind-shear detection for the TDWR system is the gust-front detection algorithm. The algorithm is designed to detect gust fronts that produce a wind-shear hazard and/or sustained wind shifts. It serves the hazard warning function by providing an estimate of the wind-speed gain for aircraft penetrating the gust front. The gust-front detection and wind-shift algorithms together serve a planning function by providing forecasted gust-front locations and estimates of the horizontal wind vector behind the front, respectively. This information is used by air traffic managers to determine arrival and departure runway configurations and aircraft movements to minimize the impact of wind shifts on airport capacity. This paper describes the gust-front detection and wind-shift algorithms to be fielded in the initial TDWR systems. Results of a quantitative performance evaluation using Doppler radar data collected during TDWR operational demonstrations at the Denver, Kansas City, and Orlando airports are presented. The algorithms were found to be operationally useful by the FAA airport controllers and supervisors.
Summary
The Federal Aviation Administration's Terminal Doppler Weather Radar (TDWR) system was primarily designed to address the operational needs of pilots in the avoidance of low-altitude wind shears upon takeoff and landing at airports. One of the primary methods of wind-shear detection for the TDWR system is the gust-front detection algorithm...
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Energy separation in signal modulations with application to speech analysis
October 1, 1993
Journal Article
Published in:
IEEE Trans. Signal Process., Vol. 41, No. 10, October 1993, pp. 3024-3051.
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Summary
Oscillatory signals that have both an amplitude-modulation (AM) and a frequency-modulation (FM) structure are encountered in almost all communication systems. We have also used these structures recently for modeling speech resonances, being motivated by previous work on investigating fluid dynamics phenomena during speech production that provide evidence for the existence of modulations in speech signals. In this paper, we use a nonlinear differential operator that can detect modulations in AM-FM signals by estimating the product of their time-varying amplitude and frequency. This operator essentially tracks the energy needed by a source to produce the oscillatory signal. To solve the fundamental problem of estimating both the amplitude envelope and instantaneous frequency of an AM-FM signal we develop a novel approach that uses nonlinear combinations of instantaneous signal outputs from the energy operator to separate its output energy product into its amplitude modulation and frequency modulation components. The theoretical analysis is done first for continuous-time signals. Then several efficient algorithms are developed and compared for estimating the amplitude envelope and instantaneous frequency of discrete-time AM-FM signals. These energy separation algorithms are then applied to search for modulations in speech resonances, which we model using AM-FM signals to account for time-varying amplitude envelopes and instantaneous frequencies. Our experimental results provide evidence that bandpass filtered speech signals around speech formants contain amplitude and frequency modulations within a pitch period. Overall, the energy separation algorithms, due to their very low computational complexity and instantaneously-adapting nature, are very useful in detecting modulation patterns in speech and other time-varying signals.
Summary
Oscillatory signals that have both an amplitude-modulation (AM) and a frequency-modulation (FM) structure are encountered in almost all communication systems. We have also used these structures recently for modeling speech resonances, being motivated by previous work on investigating fluid dynamics phenomena during speech production that provide evidence for the existence...
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Estimation of wake vortex advection and decay using meteorological sensors and aircraft data
September 28, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-201
Summary
The lift-generated wake vortices trailing behind an aircraft present a danger to aircraft following the same or nearby path. The degree of hazard to the following aircraft depends on the nature of the wake encountered in its flight path and on the ability of the aircraft to counter its effects. This report describes the current state of understanding of the factors that influence the motion and dissipation of wake vortices. The relationships of these factors to parameters that are measurable through meteorological sensors and from a priori knowledge of the vortex generating aircraft characteristics are discussed as an aid to structuring development plans for the creation of wake vortex advisory products by the Integrated Terminal Weather System (ITWS) and by special wake vortex sensors.
Summary
The lift-generated wake vortices trailing behind an aircraft present a danger to aircraft following the same or nearby path. The degree of hazard to the following aircraft depends on the nature of the wake encountered in its flight path and on the ability of the aircraft to counter its effects...
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Demonstration of GPS automatic dependent surveillance of aircraft using spontaneous Mode S beacon reports
September 22, 1993
Conference Paper
Published in:
Proc. ION-GPS-93 Sixth Int. Technical Mtg. of the Satellite Division of the Institute of Navigation, 22-24 September 1993, pp. 1-13.
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Summary
A new Automatic Dependent Surveillance (ADS) system concept combining GPS satellite navigation 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. Plans for further testing in an operational environment at Logan Airport are outlined.
Summary
A new Automatic Dependent Surveillance (ADS) system concept combining GPS satellite navigation 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...
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Integrated Terminal Weather System (ITWS) 1992 Annual Report
September 7, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-203
Summary
Hazardous weather in the terminal area is the major cause of aviation system delays as well as a principal cause of air carrier accidents. Several systems presently under development will provide significant increases in terminal safety. However, these systems will not make a major impact on weather-induced delays in the terminal area, meet a number of the safety needs (such as information to support ground deicing decisions), or reduce the workload of the terminal controller. The Integrated Terminal Weather System (ITWS) will provide improved aviation weather information in the allocated TRACON area (up to 50 nmi from the airport) by integrating data and products from various Federal Aviation Administration (FAA) and National Weather Service (NWS) sensors and weather information systems. The data from these sources will be combined to provide a unified set of safety and planning weather products for pilots, controllers, and terminal area traffic managers. by using data from multiple sensors, ITWS can generate important new products where no individual sensor alone could generate a single, reliable product. In other instances, use of data from several sources can compensate for erroneous data from one sensor and thus improve the overall integrity of existing products. Major objectives of the ITWS program are to increase the effective airport acceptance rate in adverse weather by rpoviding information to support terminal automation systems, better terminal route planning, and wake vortex advisory services, and to reduce the need for controllers to communicate weather information to pilots via VHF voice. This report summarizes the work acocmplished during fiscal year 1992 on the development of the ITWS initial operational capability products; functional prototype design; operation of testbeds to acquire data for product development and testing; operation evaluation of products by ATC users; investigation of approaches for effective transfer of the technology to the production contractor; transfer of products to pilots via digital data links; and technical support for the ITWS documents required by the General Accounting Office (GAO).
Summary
Hazardous weather in the terminal area is the major cause of aviation system delays as well as a principal cause of air carrier accidents. Several systems presently under development will provide significant increases in terminal safety. However, these systems will not make a major impact on weather-induced delays in the...
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SGS85--WGS84 transformation - interim results
August 24, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-204
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Summary
GPS and GLONASS employ different geocentric Cartesian coordinate frames to express the positions of their satellites and, therefore, of their users. GPS uses WGS84; GLONASS, SGS85. Interest in the civil aviation community in using signals from both systems requires that a transformation between the two coordinate frames be determined. We present an estimate of the SGS85--WGS84 transformation.
Summary
GPS and GLONASS employ different geocentric Cartesian coordinate frames to express the positions of their satellites and, therefore, of their users. GPS uses WGS84; GLONASS, SGS85. Interest in the civil aviation community in using signals from both systems requires that a transformation between the two coordinate frames be determined. We...
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