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Experimental measurements of low angle ground reflection characteristics at L- and C-bands for irregular terrain

November 1, 1982
  |
Project Report
Author:
David Fang-dak Sun
Published in:
MIT Lincoln Laboratory Report ATC-107
Topic:
radar
R&D area:
R&D group:

Summary

Field measurements of terrain reflection data at L band and C band have been taken during 1980 at several test sites at Hanscom airport, Fort Devens, and Camp Edwards, Massachusetts. These field data are used to (1) characterization of the L band and C band multipath environments, (2) validation of terrain mutlipath propagation models, and (3) assessment of TRSB elevation angle estimation performance with various aperture sizes. Conventional beamsum, maximum likelihood, and maximum entropy angular power spectral estimates have been employed as a means to characterize the multipath environment. The maximum entropy angular power spectral estimate offered highest resolution of the various multipath signals. The L-band field measurement results indicated that the terrain multipath were specular reflections with a high multipath levels. L-band M/D ratios ranging from -5 dB to 1 dB were observed in a variety of terrain conditions. At C band, diffuse ground reflections were evident at some measurement sites, especially at Camp Edwards J2 range site, where small scale terrain roughness was fairly visible. However, these C-band disffuse reflections appeared to be at fairly low levels, e.g., -15 dB to -20dB relative to the direct signal. The C-band peak specular multipath levels of -10dB to -2 dB were slightly lower than those of the L-band for the same terrain geometry. The phenomenon of hte "focusing" ground reflections, i.e., more than one specular ground reflection present at the same time, was observed at both L-band and C-band. For the L-band, this generally occurred in the rolling type of terrain. However, for the C-band, this also happened in the fairly flat terrain at Hanscom airport site.
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Summary

Field measurements of terrain reflection data at L band and C band have been taken during 1980 at several test sites at Hanscom airport, Fort Devens, and Camp Edwards, Massachusetts. These field data are used to (1) characterization of the L band and C band multipath environments, (2) validation of...

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Experimental measurements of low angle ground reflection characteristics at L- and C-bands for irregular terrain

Mode S Beacon System: Functional Description (Revision B)

October 27, 1982
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Project Report
Author:
Vincent A. Orlando
…
Published in:
MIT Lincoln Laboratory Report ATC-42,B
Topic:
mode S data links
R&D area:
R&D group:

Summary

This document provides a functional description of the Mode S Beacon System, a combined secondary surveillance radar (beacon) and ground-air-ground data link system capable of providing the aircraft surveillance and communications necessary to support ATC automation in future traffic environments. Mode S is capable of common-channel interoperation with the current ATC beacon system, and may be implemented at low user cost over an extended transition period. Mode S will provide the surveillance and commucation performance required by the ATC automation, the reliable communications needed to support data link services, and the capability of operating with a terminal or enroute, radar digitizer-equipped, ATC surveillance radar. The material contained in this document updates and expands the information presented in "DABS: A System Description", FAA-RD-74-189, November 1974 and "DABS: Functional Description," FAA-RD-80-41, April 1980.
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Summary

This document provides a functional description of the Mode S Beacon System, a combined secondary surveillance radar (beacon) and ground-air-ground data link system capable of providing the aircraft surveillance and communications necessary to support ATC automation in future traffic environments. Mode S is capable of common-channel interoperation with the current...

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Mode S Beacon System: Functional Description (Revision B)

TCAS I design guidelines

September 24, 1982
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Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-114
Topic:
collision avoidance
R&D area:
R&D group:

Summary

A description of the FAA airborne Traffic Alert and Collision Avoidance System known as TCAS I introduces the main topic of the report: results of an investigation of simple techniques suitable for the passive and active detection of nearby aircraft by TCAS I. This is followed by a review of the measurement facilities and data used to evaluate the detection techniques. Techniques for identifying passively detected returns from potentially threatening aircraft, i.e., the rejection or "filtering out" of non-threat aircraft, are described and evaluated. Alternatives for time-sharing the 1090 MHz channel between the TCAS I transponder and the passive detector are described. A candidate passive detector is defined and its performance is evaluated using flight test data. Predictions of the performance of a low-power TCAS I based on active detection are made via link calculations and flight test measurements. A summary of results concludes the report.
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Summary

A description of the FAA airborne Traffic Alert and Collision Avoidance System known as TCAS I introduces the main topic of the report: results of an investigation of simple techniques suitable for the passive and active detection of nearby aircraft by TCAS I. This is followed by a review of...

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TCAS I design guidelines

Mode S installation and siting criteria

September 13, 1982
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Project Report
Author:
Ronald G. Sandholm
Published in:
MIT Lincoln Laboratory Report ATC-99,REV.A
Topic:
mode S data links
R&D area:
R&D group:

Summary

This paper provides information on site-associated phenomena that affect the proper operation of a Mode S sensor and therefore warrant serious consideration when siting a sensor. The Mode S related discussion is intended to be a supplement to the ATCRBS siting criteria presented in the FAA Primary/Secondary Terminal Radar Siting Handbook. The paper discusses siting criteria as they relate to the Mode S sensor antenna system, as opposed to the ATCRBS hogtrough antenna, and importantly, addresses those characteristics of the surrounding environment that are crucial to proper Mode S surveillance.
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Summary

This paper provides information on site-associated phenomena that affect the proper operation of a Mode S sensor and therefore warrant serious consideration when siting a sensor. The Mode S related discussion is intended to be a supplement to the ATCRBS siting criteria presented in the FAA Primary/Secondary Terminal Radar Siting...

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Mode S installation and siting criteria

The AMPS computer system: design and operation

September 9, 1982
  |
Project Report
Author:
Jeffrey L. Gertz
…
Published in:
MIT Lincoln Laboratory Report ATC-110
Topic:
surveillance
R&D area:
R&D group:

Summary

The Lincoln Laboratory Air Traffic Control Radar Beacon System (ATCRBS) Monopulse Processing System (AMPS) is a mobile, stand-alone, ATCRBS surveillance sensor for processing and disseminating target reports from transponder-equipped aircraft. AMPS is essentially the ATCRBS portion of the Mode Select Beacon System (Mode S), a system designed to be an evolutionary replacement for the present third generation ATCRBS. AMPS utilizes several new features introduced by the Mode S sensor concept. In particular, the use of monopulse angle estimation permits more accurate aircraft azimuth estimation with fewer replies per scan, and improved decoding (identification) performance when garble is present. This report provides a description of the details and philosophy of the AMPS computer system implementation and operation. In particular, specific and detailed descriptions of the interrelations between AMPS's several subsystems and subtasks are provided as well as a guide on how to run them.
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Summary

The Lincoln Laboratory Air Traffic Control Radar Beacon System (ATCRBS) Monopulse Processing System (AMPS) is a mobile, stand-alone, ATCRBS surveillance sensor for processing and disseminating target reports from transponder-equipped aircraft. AMPS is essentially the ATCRBS portion of the Mode Select Beacon System (Mode S), a system designed to be an...

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The AMPS computer system: design and operation

L-Band DME multipath environment in the microwave landing system (MLS) approach and landing region

April 13, 1982
  |
Project Report
Author:
James E. Evans
Published in:
MIT Lincoln Laboratory Report ATC-116
Topic:
surveillance
R&D area:
R&D group:

Summary

The multipath environment in the approach and landing region represents an important factor in the optimization and ultimate performance of the Microwave Landing System (MLS) Precision Distance Measuring Equipment (DME/P). Various types of multipath are assessed in the context of the proposed DME/P implementation error characteristics to ascertain the principal challenges. It is shown (analytically and experimentally) that specular reflections from buildings represent a significant challenge, particularly at low altitudes (e.g., category II decision height and below) where terrain lobing can cause the effective multipath levels to exceed the effective direct signal level. However, the time delay discrimination capabilities of the proposed DME/P should effectively eliminate the bulk of such multipath. Limited S-band (3 GHz) measurements of diffuse reflections from nominally flat terrain indicated very low levels. However, specular reflections from bare, hilly terrain may present problems in some cases.
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Summary

The multipath environment in the approach and landing region represents an important factor in the optimization and ultimate performance of the Microwave Landing System (MLS) Precision Distance Measuring Equipment (DME/P). Various types of multipath are assessed in the context of the proposed DME/P implementation error characteristics to ascertain the principal...

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L-Band DME multipath environment in the microwave landing system (MLS) approach and landing region

En route weather data extraction from ATC radar systems

March 11, 1982
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Project Report
Author:
David Karp
Published in:
MIT Lincoln Laboratory Report ATC-113
Topic:
radar
R&D area:
R&D group:

Summary

This report describes the results of phase I of the En Route Radar Weather Program. The objective of this effort was to develop techniques for generating accurate en route weather reflectivity estimates in the presence of ground clutter. A candidate weather data extraction processor is proposed for use with either the ASR-MTD or ARSR-MTD radar systems. Principal features of the candidate processor include: (1) an antenna port (to permit use of an appropriate polarization), front end (with R^-2 STC) and quadrature video sampling subsystem which are separate from that used for aircraft surveillance. (2) use of a ground clutter map to select the form of clutter rejection to be used in each individual range-azimuth cell to estimate various weather reflectivity levels, and (3) spatial /temporal smoothing of the cell reflectivity estimates. The key elements of the suggested signal processing techniques were evaluated using data from MTD tests in Bedford, VA, Burlington, VT, and Atlantic City, NJ; however, the full system has not as yet received design validation/refinement and operational evaluation by ATC controllers. In particular, methods for identifying second trip weather echos should be addressed in the full system validation program.
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Summary

This report describes the results of phase I of the En Route Radar Weather Program. The objective of this effort was to develop techniques for generating accurate en route weather reflectivity estimates in the presence of ground clutter. A candidate weather data extraction processor is proposed for use with either...

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En route weather data extraction from ATC radar systems

Moving Target Detector (Mod II) summary report

November 3, 1981
  |
Project Report
Author:
David Karp
…
Published in:
MIT Lincoln Laboratory Report ATC-95
Topic:
surveillance
R&D area:
R&D group:

Summary

Under FAA sponsorship, MIT/Lincoln Laboratory has developed a second generation, field operable Moving Target Detection System (MTD-II) which has been tested at operational FAA terminal and enroute radar sites, and serves as the basis for the ASR-9 MTD technical performance specifications. This summary report covers the period October, 1976 through September, 1979 in which design, development, field testing and system performance evaluation were carried out. Report No. FAA-RD-76-190, ATC-69, "Description and Performance Evaluation of the Moving Target Detector" dated 8 March 1977, serves as the technical foundation of this work. MTD-processing design modifications were effected to handle conditions of excessive ground clutter and moving ground traffic. The rationale for the modified algorithms is provided, and measured performance characteristics at several FAA field sites are discussed.
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Summary

Under FAA sponsorship, MIT/Lincoln Laboratory has developed a second generation, field operable Moving Target Detection System (MTD-II) which has been tested at operational FAA terminal and enroute radar sites, and serves as the basis for the ASR-9 MTD technical performance specifications. This summary report covers the period October, 1976 through...

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Moving Target Detector (Mod II) summary report

ATCRBS uplink environment measurements near Jacksonville, Florida

September 25, 1981
  |
Project Report
Author:
Ferenc Nagy Jr
Published in:
MIT Lincoln Laboratory Report ATC-94
Topic:
surveillance
R&D area:
R&D group:

Summary

Airborne measurements of the Air Traffic Control Radar Beacon System (ATCRBS) 1030 MHz uplink environment are described. Measurements were made using the AMF, a special purpose airborne sensor-recorder, during a 23 May 1979 flight in the greater Jacksonville, Florida area. The 2-way flight covered the 450 nm coastline between Fayetteville (NC) and Vero Beach (FL) first at 10,000 then at 25,000 feet. Data recorded at 61 locations have been analyzed to plot combined pulse, interrogation and suppression rates for all locations and individual rates, received powers and angles for 37 locations. Fifty-nine ground interrogators were detected and a list included serves as an all-interrogator/all-location (59 x 37) visibility matrix. PRI/PRF distributions of interrogations received are shown at three selected measurement locations. A pulse-by-pulse plot of over 50 Mode 4 interrogations shows their effect on a typical transponder. A "worst" location is examined for peak instantaneous interrogation rates capable of causing transponder reply-rate limiting (RRL), desensitization and track loss. Durations and periods of recurrence of "synchronous jamming" for 23 near-equal scan periods are computed. Probabilities of multiple mainbeam coincidences ("multi-PRF jamming") are also calculated. Airborne (AMF) and ground based (FAA En-Route) coverages are compared, and reported operational problems (target splits, lost tracks, poor coverage) are addressed.
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Summary

Airborne measurements of the Air Traffic Control Radar Beacon System (ATCRBS) 1030 MHz uplink environment are described. Measurements were made using the AMF, a special purpose airborne sensor-recorder, during a 23 May 1979 flight in the greater Jacksonville, Florida area. The 2-way flight covered the 450 nm coastline between Fayetteville...

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ATCRBS uplink environment measurements near Jacksonville, Florida

Coordinated radar and aircraft observations of turbulence

May 26, 1981
  |
Project Report
Author:
Melvin Labitt
Published in:
MIT Lincoln Laboratory Report ATC-108
Topic:
weather
R&D area:
R&D group:

Summary

Interim results of a program to measure and correlate radar- and aircraft-sensed turbulence in rainstorms are presented. The dissipation factor of a turbulence air mass can be measured by an aircraft and a weather radar. Comparisons are made between precipitation reflectivity and spectral width measurements as indicators of turbulence. The instrumentation and data processing procedures are described. Examples of turbulence observations made with a storm-penetrating aircraft and the weather radar are given. The relationship between the radar observations and the physical properties of the turbulence atmosphere are derived. The relationship of radar spectral width (variance) to turbulence intensity is discussed.
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Summary

Interim results of a program to measure and correlate radar- and aircraft-sensed turbulence in rainstorms are presented. The dissipation factor of a turbulence air mass can be measured by an aircraft and a weather radar. Comparisons are made between precipitation reflectivity and spectral width measurements as indicators of turbulence. The...

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Coordinated radar and aircraft observations of turbulence
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