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DABS sensor interactions with ATC facilities

April 22, 1976
  |
Project Report
Author:
David Reiner
…
Published in:
MIT Lincoln Laboratory Report ATC-51
Topic:
surveillance
R&D area:
R&D group:

Summary

This document presents, on a functional level, the interactions that occur between a DABS sensor and an ATC facility (terminal or enroute) in order to make full use of the capabilities provided by the addition of DABS sensors to the ATC system. There are three functions of the interactions: (1) handle surveillance reports from the DABS site, (2) handle the two-way digital communications messages between pilots and controllers, and (3) handle a variety of control data messages between the two sites. For each kind of interaction, the actions taken by the DABS sensor are summerized, the messages involved in the transaction are defined, and suggestions are made concerning possible appropriate actions by the ATC facility. The latter include message generation and display, data processing, and controller and system manager activities.
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Summary

This document presents, on a functional level, the interactions that occur between a DABS sensor and an ATC facility (terminal or enroute) in order to make full use of the capabilities provided by the addition of DABS sensors to the ATC system. There are three functions of the interactions: (1)...

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DABS sensor interactions with ATC facilities

Multipath parameter computations for the MLS simulation computer program

April 8, 1976
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Project Report
Author:
Jack Capon
Published in:
MIT Lincoln Laboratory Report ATC-68
Topic:
L-band
R&D area:
R&D group:

Summary

A set of mathematical models and computer programs have been developed to characterize multipath propagation in an airport environment. When combined with system mathematical models, these models are intended to provide a firm technical basis for assessing the performance of candidate Microwave Landing Systems (MLS) in realistic airport environments. The two paramount issues in developing these models have been 1) validation based on actual field test data and 2) computer running time. The obstacles modeled include buildings and aircraft, as well as the ground which can cause both specular reflections and diffuse scattering. In addition, the shadowing effects due to runway humps, and aircraft, buildings approaching the line of sight between transmitter and receiver are included. Computational procedures are presented for obtaining the salient multipath parameters, i.e., relative magnitude, phase, directional angles, Doppler frequency, and time delay. Computer programs have been written for these algorithms using the Fortran programming language, with structured programming methods, such as Iftran, employed whenever possible. A presentation is given of computer validation data for the computational procedures. A comparison of these computer validation results with experimental field data demonstrates good agreement in all cases of interest. The computer running time for these computer programs is quite reasonable, e.g., it takes about five times longer than actual flight time to run a model of typical airport environment on an IBM 370 model 168.
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Summary

A set of mathematical models and computer programs have been developed to characterize multipath propagation in an airport environment. When combined with system mathematical models, these models are intended to provide a firm technical basis for assessing the performance of candidate Microwave Landing Systems (MLS) in realistic airport environments. The...

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Multipath parameter computations for the MLS simulation computer program

Beacon CAS (BCAS) an integrated air/ground collision avoidance system

March 23, 1976
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Project Report
Author:
Vincent A. Orlando
…
Published in:
MIT Lincoln Laboratory Report ATC-62
Topic:
surveillance
R&D area:
R&D group:

Summary

BCAS is a DABS-based airborne collision avoidance system that exploits the feature of DABS discrete addressing and integral data link. This provides for a CAS with the unique capabilities of (1) cooperative threat resolution between BCAS and conflicting aircraft through the transmission of maneuver intent (to DABS-only aircraft) and tie breaking (with other BCAS aircraft) and (2) coordination of CAS activities with the ground ATC control function through the DABS air-ground-air data link. All beacon-equipped aircraft in the vicinity of the BCAS are detected. ATCRBS-equipped aircraft are interrogated using a special Mode C interrogation. DABS aircraft are detected passively through periodic squitters emitted by all DABS transponders. Squitter-detected aircraft are tracked on altitude and only those aircraft that represent a co-altitude threat are discretely interrogated to establish a range/altitude track. The use of discrete addressing eliminates synchronous garble for the BCAS in the same manner as for DABS. This document provides a general description of BCAS from the viewpoint of its operational features and then describes the avionics package required to achieve the capability.
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Summary

BCAS is a DABS-based airborne collision avoidance system that exploits the feature of DABS discrete addressing and integral data link. This provides for a CAS with the unique capabilities of (1) cooperative threat resolution between BCAS and conflicting aircraft through the transmission of maneuver intent (to DABS-only aircraft) and tie...

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Beacon CAS (BCAS) an integrated air/ground collision avoidance system

IPC design validation and flight testing - interim results

March 16, 1976
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Project Report
Author:
John W. Andrews
…
Published in:
MIT Lincoln Laboratory Report ATC-57
Topic:
air traffic control
R&D area:
R&D group:

Summary

Intermittent Positive Control, an automated aircraft collision avoidance system requiring the participation of the aircraft pilots involved, is being evaluated in a series of live flight tests. This document provides an interim summary of the results obtained in these flight tests. Results are given for IPC algorithm design evaluation flights (34) and for pilot interaction evaluation flights (14) flown from Hanscom Field, Bedford, Massachusetts between February and October, 1975.
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Summary

Intermittent Positive Control, an automated aircraft collision avoidance system requiring the participation of the aircraft pilots involved, is being evaluated in a series of live flight tests. This document provides an interim summary of the results obtained in these flight tests. Results are given for IPC algorithm design evaluation flights...

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IPC design validation and flight testing - interim results

Experimental validation of PALM - a system for precise aircraft location

April 29, 1975
  |
Technical Report
Author:
James E. Evans
…
Published in:
MIT Lincoln Laboratory Report TN-1975-29
Topic:
air traffic control
R&D area:
R&D group:

Summary

A ground based system to precisely locate aircraft in three dimensions based on transponder replies has been designed. Field tests have been conducted to validate the design of the elevation performance. This document reports on the principle of operation, experimental hardware and field test of the Precision Altitude and Landing Monitor (PALM). The key features incorporated in the PALM design include: (a) no new avionics required, i.e., uses standard aircraft transponder; (b) high accuracy position data, i.e., a 1-mrad (0.06 degree) rms error in elevation and in azimuth; (c) broad airspace coverage, e.g., 40 degrees in elevation, 120 degrees in azimuth (expandable to 360 degrees) and several 10s of miles in range; and (d) low life cycle equipment cost. The high accuracy in the difficult airport multipath environment is a direct result of (a) newly developed antenna synthesis procedure, (b) the development of adaptive multipath suppression techniques, and (c) the use of digital signal processing. The program, to date, has focused on an experimental evaluation of the elevation performance. The electronics required for the tests have been built into a self-powered van to facilitate experiments at remote airports. The actual flight test data demonstrated experimental errors on the order of 1 mrad; moreover, as predicted by theory, the resulting errors were essentially independent of elevation angle. Potential applications for the PALM position data include parallel approach monitoring, independent altitude monitoring, and/or performance assurance monitoring of landing guidance systems.
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Summary

A ground based system to precisely locate aircraft in three dimensions based on transponder replies has been designed. Field tests have been conducted to validate the design of the elevation performance. This document reports on the principle of operation, experimental hardware and field test of the Precision Altitude and Landing...

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Experimental validation of PALM - a system for precise aircraft location

Maximum-likelihood detection of unresolved radar targets and multipath

November 1, 1974
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Journal Article
Author:
Robert J. McAulay
…
Published in:
IEEE Trans. Aerosp. Electron. Syst., Vol. AES-10, No. 6, November 1974, pp. 821-9.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Interference in the form of multipath or uncooperative targets can seriously degrade the angle-of-arrival estimation accuracy of mutiple beam processors. In this paper, the generalized likelihood ratio test is used to derive a test to detect the presence of interference for multiple beam processors. The detector performance is then analyzed in detail with respect to its dependence on signal-to-noise ratio (SNR), signal-to-interference ration (SIR), and on the relative phase between the target and interfering signals. It is shown that good detection performance can be obtained unless the phase difference between the target and interference signals is either in or out of phase.
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Summary

Interference in the form of multipath or uncooperative targets can seriously degrade the angle-of-arrival estimation accuracy of mutiple beam processors. In this paper, the generalized likelihood ratio test is used to derive a test to detect the presence of interference for multiple beam processors. The detector performance is then analyzed...

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Maximum-likelihood detection of unresolved radar targets and multipath

Prediction of optical landing guidance system performance in Cat. III-a minimum weather

November 8, 1973
  |
Technical Report
Author:
David G. Kocher
Published in:
MIT Lincoln Laboratory Report TN-1973-47
Topic:
air traffic control
R&D area:
R&D group:

Summary

The feasibility of using a laser optical system to provide precision guidance for the final two miles of aircraft landing approaches in low visibility weather is examined. Since low visibility is caused most frequently by clouds and fog, approximate calculations of the optical signal, scattered light and noise are made as a function of range for various cloud and fog densities. It is concluded that with current laser technology, performance of an optical landing guidance system would be inadequate in the presence of Category III-a minimum visibility clouds and fogs.
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Summary

The feasibility of using a laser optical system to provide precision guidance for the final two miles of aircraft landing approaches in low visibility weather is examined. Since low visibility is caused most frequently by clouds and fog, approximate calculations of the optical signal, scattered light and noise are made...

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Prediction of optical landing guidance system performance in Cat. III-a minimum weather

An optimum interference detector for DABS monopulse data editing

September 26, 1973
  |
Technical Report
Author:
Robert J. McAulay
…
Published in:
MIT Lincoln Laboratory Report TN-1973-48
Topic:
air traffic control
R&D area:
R&D group:

Summary

In the application of the Discrete Address Beacon System (DABS) concept to Air Traffic Control (ATC) surveillance, estimates of aircraft position must be made using as few replies as possible, preferably one. This requires the use of monopulse techniques. Since the beacon system provides high signal-to-noise ratios (SNR), the fundamental limitation to direction finding (DF) performance is due to externally generated interference from multipath signals and from the present Air Traffic Control Radar Beacon System (ATCRBS). Since there are many bits in any one DABS reply it should be possible to generate an accurate azimuth estimate if those that bear interference could be detected and deleted from the sample. In this report, the generalized likelihood ratio test is used to derive an optimum interference statistic. The detector performance is then analyzed in detail with respect to its dependence on SNR, interference-to-signal ratio (ISR) and on the relative phase between the target and interfering signals. It is shown that good detection performance can be obtained if the phase difference between the target and interference signals are either in- or out-of-phase.
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Summary

In the application of the Discrete Address Beacon System (DABS) concept to Air Traffic Control (ATC) surveillance, estimates of aircraft position must be made using as few replies as possible, preferably one. This requires the use of monopulse techniques. Since the beacon system provides high signal-to-noise ratios (SNR), the fundamental...

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An optimum interference detector for DABS monopulse data editing

The effects of interference on monopulse performance

August 1, 1973
  |
Technical Report
Author:
Robert J. McAulay
Published in:
MIT Lincoln Laboratory Report TN-1973-30
Topic:
air traffic control
R&D area:
R&D group:

Summary

The first and second moments of the monopulse azimuth estimates are used to characterize the estimator performance in a background of mainbeam or sidelobe multipath or ATCRBS interference. An exact expression for the bias error is obtained that not only accounts for the bias due to targets separated in azimuth but also demonstrates the effect of fading or signal cancellation. For a target signal at a 20 dB signal-to-noise ratio, it is shown that the fading effect produces negligible bias unless the signal-to-interference ratio is between ±2.5 dB. A first order expression for the variance is obtained that demonstrates that an increase in the random error will occur due to the target separation in azimuth and due to signal fades. The exact nature of the bias and variance depend strongly on the relative phase between the target and interference signals with the poorest performance being obtained at the in- and out-of-phase conditions. It is knowledge of this behavior that is essential in evaluating the idea of azimuth estimation data editing.
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Summary

The first and second moments of the monopulse azimuth estimates are used to characterize the estimator performance in a background of mainbeam or sidelobe multipath or ATCRBS interference. An exact expression for the bias error is obtained that not only accounts for the bias due to targets separated in azimuth...

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The effects of interference on monopulse performance

A decision-directed adaptive tracker

January 1, 1973
  |
Journal Article
Author:
Robert J. McAulay
…
Published in:
IEEE Trans. Aerosp. Electron. Syst., Vol. AEM-9, No. 2, March 1974, p. 229-236.
Topic:
air traffic control
R&D area:
R&D group:

Summary

In the design of a tracking filter for air traffic control (ATC) applications, a maneuvering aircraft can be modelled by a linear system with random noise accelerations. A Kalman filter tracker, designed on the basis of a variance chosen according to the distribution of the potential maneuver accelerations, will maintain track during maneuvers and provide some improvement in position accuracy. However, during those portions of the flight path where the aircraft is not maneuvering, the tracking accuracy will not be as good as if no acceleration noise had been allowed in the tracking filter. In this paper, statistical decision theory is used to derive an optimal test for detecting the aircraft maneuver: a more practical suboptimal test is then deduced from the optimal test. As long as no maneuver is declared, a simpler filter, based on a constant-velocity model, is used to track the aircraft. When a maneuver is detected, the tracker is reinitialized using stored data, up-dated to the present time, and then normal tracking is resumed as new data arrives. In essence, the tracker performs on the basis of a piecewise linear model in which the breakpoints are defined on-line using the maneuver detector. Simulation results show that there is a significant improvement in tracking capability using the decision-directed adaptive tracker.
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Summary

In the design of a tracking filter for air traffic control (ATC) applications, a maneuvering aircraft can be modelled by a linear system with random noise accelerations. A Kalman filter tracker, designed on the basis of a variance chosen according to the distribution of the potential maneuver accelerations, will maintain...

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A decision-directed adaptive tracker
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