Publications
Automatic dependent surveillance broadcast via GPS-squitter: a major upgrade to the National Airspace System
April 18, 1995
Conference Paper
Published in:
SPIE, Vol. 2464, Air Traffic Control Technologies, 18-19 April 1995, pp. 2-13.
Summary
GPS-Squitter is a technology for Surveillance of aircraft via broadcast of their GPS-determined positions to all listeners, using the Mode S data link. It can be used to provide traffic displays, on the ground for controllers and in the cockpit for pilots, and will enhance TCAS performance. It is compatible with the existing ground-based beacon interrogator radar system and is an evolutionary way to move from ground-based-radar surveillance to satellite-based surveillance. GPS-Squitter takes advantage of the substantial investment made by the U.S. in the powerful GPS position-determining system and has the potential to free the Federal Aviation Administration from having to continue maintaining a precise position-determining capability in ground-based radar. This would permit phasing out the ground-based secondary surveillance radar system over a period of 10 to 20 years and replacing it with much simpler ground stations, resulting in cost savings of hundreds of millions of dollars.
Summary
GPS-Squitter is a technology for Surveillance of aircraft via broadcast of their GPS-determined positions to all listeners, using the Mode S data link. It can be used to provide traffic displays, on the ground for controllers and in the cockpit for pilots, and will enhance TCAS performance. It is compatible...
READ MORE
Initial evaluation of the Oregon State University Planetary Boundary Layer Column Model for ITWS applications
April 13, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-233
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of products important for air traffic control in the terminal area. Some ITWS is supporting the development of products important for air traffic control in the terminal area. Some ITWS products will allow air traffic managers to anticipate operationally significant short-term (0-30 min) changes in ceiling and visibility (C&V) and aircraft separations necessary to avoid encounters with wake vortices. Development of such products exploits data that will be available from new FAA terminal area sensor systems. These sensor systems include Terminal Doppler Weather Radar (TDWR), Next Generation Weather Radar (NEXRAD), the Meteorological Data Collection and Reporting System (MDCRS), and the Automated Surface Observing System (ASOS). A Dynamic Atmospheric Vertical Structure Nowcast System (DAVS-NS) is being developed that will add value to ITWS by providing current analyses and short-term forecasts of the vertical atmospheric structure focused at specific sites within the terminal domain. This report summarizes the initial evaluation of the Oregon State University one-dimensional boundary layer model for its potential role within a DAVS-NS.
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of products important for air traffic control in the terminal area. Some ITWS is supporting the development of products important for air traffic control in the terminal area. Some ITWS products will allow air traffic managers...
READ MORE
TCAS III bearing error evaluation
April 13, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-231
Summary
TCAS III seeks to enhance TCAS II by providing resolution advisory (RA) capability in the horizontal plane. Additionally, elimination of nuisance RAs through the use of miss distance filtering (MDF) are sought to make TCAS more compatible within the airspace. Both functions (horizontal RAs and MDF) are enabled with accurate estimates of the horizontal miss distance. TCAS III estimates of miss distance rely on range and bearing measurements derived from intruder aircraft replies. Large errors in the TCAS bearing measurement can be introduced by the airframe structure and other antennas in the vicinity of the TCAS antenna. These large bearing errors can result in large miss distance estimation errors, which will directly affect the performance of the horizontal RA and MDF operation. In evaluating the performance of the bearing measurements, measurements of the bearing error were used in a simulation of TCAS III surveillance and collision avoidance functions to assess their effect on performance. The performance was evaluated by examining (1) the expected percentage of horizontal RAs issued, (2) the expected reduction in nuisance RAs by the MDF, and (3) the reliability of the monitoring process during a horizontal RA maneuver.
Summary
TCAS III seeks to enhance TCAS II by providing resolution advisory (RA) capability in the horizontal plane. Additionally, elimination of nuisance RAs through the use of miss distance filtering (MDF) are sought to make TCAS more compatible within the airspace. Both functions (horizontal RAs and MDF) are enabled with accurate...
READ MORE
Integrated Terminal Weather System (ITWS) demonstration and validation operational test and evaluation
April 13, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-234
Summary
During summer 1994, MIT Lincoln Laboratory conducted the Operational Test and Evaluation Demonstration and Validation (Dem Val) of the Federal Aviation Administration's Integrated Terminal Weather System (ITWS). The purpose of the demonstration was to obtain user feedback on products and to prove that the ITWS products and concept were sufficiently mature to proceed with procurement. Dem Val was conducted at the Memphis International Airport from 23 May through 22 July and at the Orlando International Airport from 11 July through 19 August. Products were delivered to users at the Memphis Airport Traffic Control Tower (ATCT) and TRACON (Terminal Radar Approach Control), at the Memphis Air Route Traffic Control Center (ARTCC), at the Orlando International ATCT and TRACON, and at the Jacksonville ARTCC. In addition, ITWS displays were available to the National Weather Service forecast offices at Memphis, TN, and Melbourne, FL; to Northwest Airlines in Minneapolis, MN; and to Delta Airlines in Orlando, FL. This report documents the technical performance of the product generation algorithms. Each algorithm is described briefly, including the product operational and display concepts. The techniques by which the technical performance is assessed and the results of the assessment are presented. The performance of the algorithms is measured against the Minimum Operational Performance Requirements (MOPR), which products must meet to be considered operationally useful by the ATC user community.
Summary
During summer 1994, MIT Lincoln Laboratory conducted the Operational Test and Evaluation Demonstration and Validation (Dem Val) of the Federal Aviation Administration's Integrated Terminal Weather System (ITWS). The purpose of the demonstration was to obtain user feedback on products and to prove that the ITWS products and concept were sufficiently...
READ MORE
GPS-squitter interference analysis
April 6, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-229
Summary
GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits equipped aircraft to participate in ADS and/or beacon ground environments, offering many possibilities for transition from a beacon to an ADS-based environment. Since GPS-Squitter and its associated data link share the 1030/1090-MHz beacon frequencies with other users (e.g., ground beacon radars and TCAS), there is some level of interaction between the operation of these various systems. One form of interaction is the effect on GPS-Squitter operation caused by the activities of other users. This effect, plus the effect of self-interference of GPS-Squitter operation, determines the operational capacity of GPS-Squitter. The complementary process is the effect of the GPS-Squitter operation on the other users of the beacon frequencies. This report provides an analysis of the interference to the other users of the 1030/1090-MHz beacon frequencies caused by GPS-Squitter operation. The principal interference effect is channel occupancy on the beacon frequencies that prevents the reception of a desired signal by a receiver. The basis for the analysis is to estimate the channel occupancy on the beacon frequencies and its effect on the operation of victim receivers on those frequencies. The analysis is performed separately for the two frequencies. The analysis of 1030-MHz interference estimates the effect of the 1030-MHz data link activity that may be associated with GPS-Squitter (such as differential correction broadcast and two-way data link) on the operation of a transponder receiver. The 1090-MHz analysis estimates similar interference effects on (1) a terminal or en route sensor receiver and (2) a TCAS receiver. The results indicate that the operation of GPS-Squitter and its associated data link will have a negligible effect on the other users of these frequencies.
Summary
GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits...
READ MORE
Large population speaker identification using clean and telephone speech
March 1, 1995
Journal Article
Published in:
IEEE Signal Process. Lett., Vol. 2, No. 3, March 1995, pp. 46-48.
Topic:
R&D area:
Summary
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 TIMIT results show large population performance under near-ideal conditions, and the NTIMIT results show the corresponding accuracy loss due to telephone transmission. These are 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% were achieved on the TIMIT and NTIMIT databases, respectively.
Summary
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 TIMIT results...
READ MORE
GPS-squitter channel access analysis
February 14, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-230
Summary
GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits equipped aircraft to participate in ADS and/or beacon ground environments, offering many possibilities for transition from a beacon to an ADS-based environment. A number of choices exist in the selection of the squitter channel access protocol, including the access technique (i.e., random or organized), as well as such issues as the rate of squitter transmissions and whether they are fixed or variable. This report provides an analysis of the performance of the channel access protocol selected for GPS-Squitter compared with other alternative approaches. The results of this analysis indicate that the performance of the selected protocol is superior to the defined alternatives.
Summary
GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits equipped aircraft to participate in ADS and/or beacon ground environments, offering many possibilities for transition from...
READ MORE
The enhanced Airborne Measurement Facility recording system
January 31, 1995
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-228
Summary
The Airborne Measurement Facility (AMF) is a data collection system that receives and records pulse and other information on the 1030/1090-MHz frequencies used by the FAA's secondary surveillance radar and collision avoidance systems. These systems include the Air Traffic Control Radar Beacon System (ATCRBS), the Mode Select (Mode S) Beacon System, and the Traffic Alert and Collision Avoidance System (TCAS). Designed and constructed by MIT Lincoln Laboratory in the 1970s, this unique measurement tool has been used to conduct advanced research in beacon-based air traffic control (ATC) over the past 20 years. The original AMF included a recorder capable of recording at the maximum rate of 2 Mbits/sec. Although this recording system worked well, it had become difficult to maintain in recent years. In 1993, the Air Traffic Surveillance Group, with support from the FAA, decided to incorporate the latest tape recording technology into an enhanced AMF recording system. The main purpose of this report is to provide guidance to analysts for AMF operation and data analysis. Finally, this report complements an AMF User's Manual, which is a more detailed document for using and maintaining the AMF.
Summary
The Airborne Measurement Facility (AMF) is a data collection system that receives and records pulse and other information on the 1030/1090-MHz frequencies used by the FAA's secondary surveillance radar and collision avoidance systems. These systems include the Air Traffic Control Radar Beacon System (ATCRBS), the Mode Select (Mode S) Beacon...
READ MORE
An algorithm to remove anomalous propagation clutter returns from ASR-9 weather channel data using pencil beam radar data
January 15, 1995
Conference Paper
Published in:
Sixth Conf. on Aviation Weather Systems, 15-20 January 1995, pp. 366-371.
Topic:
R&D area:
R&D group:
Summary
The Integrated Terminal Weather System (ITWS), currently under development by the Federal Aviation Administration (FAA), will 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 sensors as well as from aircraft in flight in the terminal area. The ITWS will provide products to Air Traffic personnel that are immediately usable without further meteorological interpretation. These products include current terminal-area weather and short-term (0-30 minute) predictions of significant weather phenomena. The ASR (Airport Surveillance Radar)-9 radar is used in the terminal area to control aircraft. This radar has a weather channel that provides the location and intensity of precipitation (6-level) on the air traffic controllers' radar screen. Controllers use the weather information to aid aircraft in avoiding weather. The ASR-9 radar data are often contaminated by anomalous propagation (AP). Due to the smoothing process used in the ASR-9, controllers are unable to distinguish between AP and valid weather returns. As a result controllers may attempt to vector aircraft around AP, resulting in increased controller workload and decreased terminal airspace capacity. The ITWS product suite includes two precipitation products: ITWS Precipitation (AP removed) and the ASR-9 Precipitation (AP flagged in black). The basis for these products is the ASR-9 weather channel output. Both of these products are created by an algorithm called AP-edit. The ITWS precipitation product is a representation of the location and intensity of precipitation in the TRACON (Terminal Radar Approach Control) area and may be used for situational awareness and as a planning aid for air traffic managers by showing where weather is located relative to traffic flow patterns. The ASR-9 precipitation product explicitly shows where AP clutter is located relative to any ASR-9 radar. Since the ITWS precipitation product docs not replace the ASR-9 weather display on any controllers' displays, the Air Traffic Control (ATC) supervisor or traffic manager may use the ASR-9 precipitation product to indicate the location of AP clutter to any individual controller. The products were demonstrated during the ITWS Demonstration and Validation Operational Test and Evaluation (OT&E) conducted at Memphis and Orlando International Airports during the summer of 1994. This paper describes the AP-edit algorithm and provides a preliminary evaluation of the performance of the algorithm.
Summary
The Integrated Terminal Weather System (ITWS), currently under development by the Federal Aviation Administration (FAA), will 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 sensors as...
READ MORE
Applications of column models for terminal weather nowcasts
January 15, 1995
Conference Paper
Published in:
Sixth Conf. on Aviation Weather Systems, 15-20 January 1995, pp. 66-71.
Topic:
R&D area:
R&D group:
Summary
The Planetary Boundary Layer (PBL) is that part of the atmosphere, which is directly influenced by the presence of the earth's surface, and which responds to surface forcing with a time-scale of an hour or less. The Residual Layer (RL) is the portion of the lower atmosphere, which was part of the PBL within the past several hours, and which has become separated from the influence of short-term surface forcing, usually by the formation of a cooler layer at the surface. In the mid-latitudes, the height of the combined PBL and RL is usually 1-2 kilometers. A column model is a one-dimensional prognostic model for the state of a single column of the atmosphere, with special attention to the processes in the lowest few kilometers. It is designed to diagnose and nowcast the vertical structure of the PBL. Important information for ITWS1 nowcast products are the vertical profiles of horizontal wind velocity, temperature, humidity, and turbulent kinetic energy (TKE) in the lowest few kilometers (Sankey, 1994). Traditionally, operational meteorologists have obtained estimates of these quantities by balloon soundings, a measurement process that is not well-suited for continuous updates. We are investigating the possibility of developing an operational column model to obtain this vertical structure information for use in the ITWS. Our approach involves using a combination of sensing technology and analysis techniques that have proven successful in several research programs. Column models are designed to mimic the processes by which the surface forces the processes in the low atmosphere at times when local radiation is a dominant factor. Fluxes are measures of the net rates of these transport processes. The widely used Oregon State University column model (OSUlDPBL) parameterizes the fluxes by gradient transfer techniques (Troen and Mahr!, 1986). This model has provided dependable service in several field experiments, providing information with a vertical resolution of tens of meters. It is not designed to provide a fine-scale description of the stable nocturnal PBL. The French model COB EL has been developed to forecast the occurrence of radiation fog, and therefore concentrates on modeling the stable nocturnal PBL (Bergot and Guedalia, 1994). It uses a prognostic equation to estimate TKE in the stable boundary layer and parameterizes the fluxes in tern1s of the TKE (Duynkerke, 1991). A discussion of the potential uses of the column model in the ITWS is followed by the considerations that motivate the design of an operational column model. The prototype design is described. We conclude with the results of a preliminary evaluation using STORMFEST data (STORM Project Office, 1992) and a discussion of plans for a more comprehensive evaluation.
Summary
The Planetary Boundary Layer (PBL) is that part of the atmosphere, which is directly influenced by the presence of the earth's surface, and which responds to surface forcing with a time-scale of an hour or less. The Residual Layer (RL) is the portion of the lower atmosphere, which was part...
READ MORE