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Radar detection of thunderstorm hazards for air traffic control volume I: storm cell detection

October 7, 1976
  |
Project Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report ATC-67,I
Topic:
weather
R&D area:
R&D group:

Summary

A procedure was developed to detect hazardous regions within thunderstorms using weather radar data. The procedure is based upon the hypothesis that convective turbulence occurs within 2-3 km of relative radar reflectivity maxima (cells). The hypothesis was tested using a limited set of simultaneous aircraft and radar data. Good agreement was found between the observed regions of convective turbulence and the cell locations determined by radar. The viability of the hazard detection hypothesis as a basis for automatic warning and forcast depends upon the reliability of the cell detection and tracking algorithms. Analysis of precision radar data revealed that the cells are small in area extent, have a detection probability in excess of 0.9 using multiple radar scans, and are readily tracked for periods between 10 and 20 minutes. The characteristics of radar systems for acquiring data to support cell detection, are discussed. The role of Doppler spectral data is explored, and it is found that practical limitations on radar beamwidth hamper direct observation of turbulence on the scale size hazardous to aircraft.
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Summary

A procedure was developed to detect hazardous regions within thunderstorms using weather radar data. The procedure is based upon the hypothesis that convective turbulence occurs within 2-3 km of relative radar reflectivity maxima (cells). The hypothesis was tested using a limited set of simultaneous aircraft and radar data. Good agreement...

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Radar detection of thunderstorm hazards for air traffic control volume I: storm cell detection

Empirical characterization of IPC tracker performance using DABS data

June 9, 1976
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Project Report
Author:
John L. Leeper
…
Published in:
MIT Lincoln Laboratory Report ATC-61
Topic:
surveillance
R&D area:
R&D group:

Summary

The performance of a set of tracker algorithms proposed for use in the DABS-based Intermittent Positive Control (IPC) collision avoidance system is assessed. The position projecting tracker algorithms are subjected to actual surveillance data obtained at the Lincoln Laboratory DABS Experimental Facility. Effects of turn-rate, speed, wind and surveillance accuracy upon heading error, speed error and position error are presented.
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Summary

The performance of a set of tracker algorithms proposed for use in the DABS-based Intermittent Positive Control (IPC) collision avoidance system is assessed. The position projecting tracker algorithms are subjected to actual surveillance data obtained at the Lincoln Laboratory DABS Experimental Facility. Effects of turn-rate, speed, wind and surveillance accuracy...

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Empirical characterization of IPC tracker performance using DABS data

Low elevation angle measurement limitations imposed by the troposphere - and analysis of scintillation observations made at Haystack and Millstone

May 18, 1976
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TR-518
Topic:
radar
R&D area:
R&D group:

Summary

Tropospheric angle-of-arrival and amplitude scintillation measurements were made at X-band (7.3 GHz) and at UHF (0.4 GHz). The measurements were made using sources on satellites with 12-day orbits. The angle of arrival of the ray path to a satellite changed slowly allowing observations of fluctuations caused by atmospheric irregularities as they slowly drifted across the ray path. The fluctuations were characterized by the rms variations of elevation angle and the logarithm of received power (log power). Over a one-year period, 458 hours of observation were amassed spanning every season, time of day, and weather conditions. The results show strong scintillation occurrences below 1 to 2 degrees elevation angles characterized by a number of random occurrences of multipath events that produce deep fades, angle-of-arrival fluctuations, and depolarization of the received signal. The log power fluctuations ranged from 1 to 10 dB rms at elevation angles below 2 degrees to less than 0.1 dB at elevation angles above 10 degrees. The elevation angle fluctuations ranged from 1 to 100 mdeg at elevation angles below 2 degrees to less than 5 mdeg at a 10 degrees elevation angle. Comparable fluctuations in elevation angle are expected for bias refraction correction models based upon the use of surface values of the refractive index.
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Summary

Tropospheric angle-of-arrival and amplitude scintillation measurements were made at X-band (7.3 GHz) and at UHF (0.4 GHz). The measurements were made using sources on satellites with 12-day orbits. The angle of arrival of the ray path to a satellite changed slowly allowing observations of fluctuations caused by atmospheric irregularities as...

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Low elevation angle measurement limitations imposed by the troposphere - and analysis of scintillation observations made at Haystack and Millstone

PALM - a system for precise aircraft location

May 16, 1976
  |
Journal Article
Author:
Irvin G. Stiglitz
…
Published in:
J. of the Institute of Navigation, Vol. 23, No. 3, Fall 1976, pp. 257-261.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The Precision Altitude and Landing Monitor (PALM) is intended to provide accurate stand-alone three-dimensional position data for aircraft equipped with standard beacon transponders using ground equipment designed for low life cycle cost. The PALM program, to the present time, has focused on an experimental evaluation of the accuracy of elevation measurements. The results of these measurements have successfully validated the theoretical prediction of a 1-mrad (0.06 degree) elevation accuracy at low elevation angles. The key features in the PALM design include (1) No new avionics required, i.e., it uses standard aircraft transponder. IFPALM is used as the data base for certain ground-to-air messages, a standard VHF or DABS data link could be employed. (2) High accuracy position data, i.e., a 1-mrad rms error in elevation and in azimuth at low elevation angles. (3) Broad airspace coverage, e.g., 40 degrees in elevation, 120 degrees in azimuth (expandable to 360 degrees), and several tens of miles in range. (4) Low life cycle equipment cost, i.e., it incorporates a fixed passive receiving antenna array and a minicomputer to perform the signal processing necessary for interference rejection.
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Summary

The Precision Altitude and Landing Monitor (PALM) is intended to provide accurate stand-alone three-dimensional position data for aircraft equipped with standard beacon transponders using ground equipment designed for low life cycle cost. The PALM program, to the present time, has focused on an experimental evaluation of the accuracy of elevation...

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PALM - a system for precise aircraft location

Advances in radar signal processing

May 14, 1976
  |
Conference Paper
Author:
Charles E. Muehe
Published in:
Electro/76, 11-14 May 1976.
Topic:
radar
R&D area:
R&D group:

Summary

The recent availability of new solid-state digital components has made possible the development of radar signal processing techniques only dreamed of in the past. The philosophy and design of these techniques is described in terms of a new signal processor for Airport Surveillance Radars called the Moving Target Detector (MTD). Test results showing greatly improved automatic aircraft acquisition and tracking are discussed.
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Summary

The recent availability of new solid-state digital components has made possible the development of radar signal processing techniques only dreamed of in the past. The philosophy and design of these techniques is described in terms of a new signal processor for Airport Surveillance Radars called the Moving Target Detector (MTD)...

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Advances in radar signal processing

Spectra of ionospheric scintillation

May 1, 1976
  |
Journal Article
Author:
Robert K. Crane
Published in:
J. Geophys. Res., Vol. 81, No. 13, 1 May 1976, pp. 2041-2050.
Topic:
radar
R&D area:
R&D group:

Summary

Observation of amplitude and phase scintillation were made at the Millstone Hill radar facility by using phase coherent sources at 150 and 400 MHz on the U.S. Navy navigation system satellites. These observations have been processed to yield power spectra of the fluctuations in the logarithm of the received power (log power) at each frequency and the calculations in phase path length difference (differential phase) between the two frequencies. A theoretical analysis was performed to predict the log power and differential phase power spectra. The theoretical model was based upon weak scatter theory for a thick screen with a three-dimensional power law power spectrum representation for the electron density fluctuations. A -4 exponent for the power law best fit the observed spectra. For weak scintillation (rms fluctuations in log power less than 5 dB or S4 < 0.9) the theroretical calculations were in excellent agreement with the observations. For strong scintillation, saturation was observed, and the measured spectra were broader than those predicted on the basis of weak scatter theory. An increase in electron density fluctuations relative to the value predicted by the power law model was observed at scale sizes smaller than 0.8 km.This increase may be responsible for the anomalous scintillation observations at gigahertz frequencies.
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Summary

Observation of amplitude and phase scintillation were made at the Millstone Hill radar facility by using phase coherent sources at 150 and 400 MHz on the U.S. Navy navigation system satellites. These observations have been processed to yield power spectra of the fluctuations in the logarithm of the received power...

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Spectra of ionospheric scintillation

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

Concept and plan for the development of a weather support subsystem for Air Traffic Control

April 16, 1976
  |
Project Report
Author:
Steven I. Krich
…
Published in:
MIT Lincoln Laboratory Report ATC-64
Topic:
weather
R&D area:
R&D group:

Summary

This report summarizes the results of a study to: (1) investigate the primary needs of air traffic controllers, flow controllers, and central flow controllers for weather information, (2) define a cost effective system concept to meet these needs, and (3) lay out a plan for the development of the proposed weather subsystem to support Air Traffic Control. The recommended system will provide rapid geration and dissemination of reliable use oriented observations and very short range severe weather forecasts (up to 30 min.) to facilitate controller planning. This new capability will: 1) reduce weather induced controller work load peaks, 2) permit controllers to coordinate and preplan aircraft rerouting for weather avoidance, 3) achieve an improved balance between the inefficiency of overreaction and the essentials of safety, 4) facilitate controller response to pilot requests for weather data on a work load permitting basis, and 5) enable the issuance of accurate weather advisories. The system will also provide rapid generation and dissemination of reliable short range forecasts (up to 4 hours) to permit early introduction of necessary flow control procedures. This new capability will: 1) decrease problems for controllers, 2) increase acceptance of flow control, and 3) increase traffic flow efficiency without decreasing safety.
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Summary

This report summarizes the results of a study to: (1) investigate the primary needs of air traffic controllers, flow controllers, and central flow controllers for weather information, (2) define a cost effective system concept to meet these needs, and (3) lay out a plan for the development of the proposed...

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Concept and plan for the development of a weather support subsystem for Air Traffic Control

Multipath parameter computations for the MLS simulation computer program

April 8, 1976
  |
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

The Airborne Measurement Facility (AMF) system description

March 25, 1976
  |
Project Report
Author:
George V. Colby
Published in:
MIT Lincoln Laboratory Report ATC-60
Topic:
air traffic control
R&D area:
R&D group:

Summary

The Airborne Measurement Facility (AMF) is a data collection and conversion system that provides a means for obtaining recorded data representing pulsed electromagnetic signals received on one of the two ATC radar beacon frequency bands that is selected for a given data collecting mission. The facility consists of two subsystems: (1) an airborne subsystem which collects and records data during flight, and (2) a ground playback facility which processes the data and transcribes it onto computer-compatible tape.
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Summary

The Airborne Measurement Facility (AMF) is a data collection and conversion system that provides a means for obtaining recorded data representing pulsed electromagnetic signals received on one of the two ATC radar beacon frequency bands that is selected for a given data collecting mission. The facility consists of two subsystems...

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The Airborne Measurement Facility (AMF) system description
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