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DABS monopulse summary

February 4, 1977
  |
Project Report
Author:
David Karp
…
Published in:
MIT Lincoln Laboratory Report ATC-72
Topic:
surveillance
R&D area:
R&D group:

Summary

Improved azimuthal resolution of proximate aircraft necessary to support ATC automation can be achieved by beacon surveillance systems employing monopulse angle estimation techniques described in this report. Included in the report are the results of beacon surveillance monopulse system analyses relating to off-boresight angle estimation using short (1/2 micro sec) pulses: the effects of specular and diffuse multipath signal return; the effects of overlapping ATCRBS fruit replies, and the problems of antenna pattern design. These topics have been studied in detail as part of the Lincoln Laboratory disign of the Discrete Address Beacon System (DABS). This report summarizes analytical results obtained. In general, it has been concluded that the ATC environment does not pose a serious problem to the use of the monopulse concept for beacon system direction finding and that sufficient direction finding accuracy can be obtained using a small number of narrow pulses for each scan.
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Summary

Improved azimuthal resolution of proximate aircraft necessary to support ATC automation can be achieved by beacon surveillance systems employing monopulse angle estimation techniques described in this report. Included in the report are the results of beacon surveillance monopulse system analyses relating to off-boresight angle estimation using short (1/2 micro sec)...

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DABS monopulse summary

Ionospheric scintillation

February 1, 1977
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Journal Article
Author:
Robert K. Crane
Published in:
Proc. of the IEEE, Vol. 65, No. 2, February 1977, pp. 180-199.
Topic:
radar
R&D area:
R&D group:

Summary

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence distribution functions which show that scintillation phenomena significantly affect the design of transionospheric radar or communication systems operating at frequencies below 1 GHz. Diversity schemes useful for mitigation of scintillation effects are considered. Mention is made of the geophysical processes thought to be responsible for scintillation.
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Summary

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence...

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Ionospheric scintillation

ATCRBS mode of DABS

January 31, 1977
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Project Report
Author:
Jeffrey L. Gertz
Published in:
MIT Lincoln Laboratory Report ATC-65
Topic:
surveillance
R&D area:
R&D group:

Summary

The Discrete Address Beacon System (DABS) has been designed to be an evolutionary replacement oth the third generation Air Traffic Control Radar Beacon System (ATCRBS). Although the ATCRBS returns processed by DABS will be identical to those currently being employed, the DABS processing system will not merely mimic the present system. Instead, it has been designed to surpass current performance levels even while reducing the number of interrogations transmitted per scan. This will be made possible by utilizing the availability of several new features introduced by the DABS sensor. In particular, the employment of monopulse antenna will permit both more accurate azimuth estimation with fewer replies per scan and improved decoding performance when garble is present. The ATCRBS portion of the DABS sensor has been designed to be a complete, self-contained package that performs all ATCRBS functions required for aircraft surveillance. The major tasks it implements are: 1. Determining the range, azimuth, and code of each received ATCRBS reply 2. Grouping replies from the same aircraft into target reports and discarding fruit replies 3. Identifying all false alarm target reports due to reflections, coincident fruit, splitting, or ringaround 4. Initiating and maintaining a track on all aircraft in the covered airspace The first function has been implemented in hardware while the remaining ones are performed in software. This report will discuss in detail only the software subsystems. The ATCRBS system described in this report has been implemented in the ATCRBS Monopulse Processing System (AMPS) built at Lincoln Laboratory. Although the AMPS design is based upon the specifications contained in the DABS Engineering Requirements (ER), there are two major differences between AMPS and the ER system. First, the design described here is for a standalone ATCRBS system; no capabilities are built in to send, receive, or employ information from other sensors, and no formal interfaces to other ATC functions are defined. Second, this system was not intended to be a production prototype, so no reliability features have been included.
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Summary

The Discrete Address Beacon System (DABS) has been designed to be an evolutionary replacement oth the third generation Air Traffic Control Radar Beacon System (ATCRBS). Although the ATCRBS returns processed by DABS will be identical to those currently being employed, the DABS processing system will not merely mimic the present...

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ATCRBS mode of DABS

Automatic Reporting of Height (AROH) design and trade-off studies

November 1, 1976
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Technical Report
Author:
Lincoln Cartledge
…
Published in:
MIT Lincoln Laboratory Report TN-1976-42
Topic:
air traffic control
R&D area:
R&D group:

Summary

Application of MTD signal processing and state-of-the-art data processing can result in a completely automatic nodding beam height finder. The resulting savings in manpower are significant. Calculations show that such a system should have good sensitivity and adequate rejection of ground and weather clutter. Modification of an FPS-6 radar for this purpose is discussed.
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Summary

Application of MTD signal processing and state-of-the-art data processing can result in a completely automatic nodding beam height finder. The resulting savings in manpower are significant. Calculations show that such a system should have good sensitivity and adequate rejection of ground and weather clutter. Modification of an FPS-6 radar for...

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Automatic Reporting of Height (AROH) design and trade-off studies

The PMP, a programmable radar signal processor

October 7, 1976
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Conference Paper
Author:
Bruce G. Laird
…
Published in:
Monthly Mtg. of Boston IEEE, Mitre Corp, Bedford, Ma 13 October 1976.
Topic:
signal processing
R&D area:
R&D group:

Summary

During the last few years, the Radar Techniques Group at Lincoln Laboratory has been applying digital processing techniques to the problem of automatic detection of moving vehicles in the presence of ground and weather clutter. An outgrowth of this effort is the development of a real-time radar signal processor, the Parallel Microprogrammable Processor, or PMP. Conceptually the PMP consists of a single control unit and an array of identical processing modules. The control unit sequences through a program stored in its control memory, providing identical instructions to each processing module, so that all modules are performing the same operation in parallel, each on its own set of data. The talk will focus on the motivation for, and advantages of such a parallel architecture, as presently implemented with TTL medium-scale integrated circuits. Some examples of parallel computation will be illustrated as well as more general issues relating to programmability of the PMP. Much of the information in the talk will be based on experience with an operational prototype, which has a control unit and one processor module.
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Summary

During the last few years, the Radar Techniques Group at Lincoln Laboratory has been applying digital processing techniques to the problem of automatic detection of moving vehicles in the presence of ground and weather clutter. An outgrowth of this effort is the development of a real-time radar signal processor, the...

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The PMP, a programmable radar signal processor

Radar detection of thunderstorm hazards for air traffic control volume II: radar systems

October 7, 1976
  |
Project Report
Author:
Steven M. Sussman
Published in:
MIT Lincoln Laboratory Report ATC-67,II
Topic:
weather
R&D area:
R&D group:

Summary

Radar systems are investigated for the acquisition of weather data to support detection and forecasting of hazardous turbulence associated with individual storm cells. Utilization of the FAA Airport Surveillance Radar (ASR) is explored. The issues of antenna polarization and Sensitivity Time Control (STG) that impact on shared operation for aircraft and weather detection are addressed. Candidate system configurations employing a common RF channel and dual orthogonal polarization channels are discussed. Ground clutter discrimination by coherent Doppler and noncoherent (Doppler spread) processing methods is described. An interim procedure is suggested for obtaining fixed reflectivity contour data from a Moving Target Detector for use in the all-digital ARTS. A preliminary design is presented for a new joint-use, long-range weather radar to support enroute air traffic controllers and to meet the data requirements of the National Weather Service and the Air Weather Service.
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Summary

Radar systems are investigated for the acquisition of weather data to support detection and forecasting of hazardous turbulence associated with individual storm cells. Utilization of the FAA Airport Surveillance Radar (ASR) is explored. The issues of antenna polarization and Sensitivity Time Control (STG) that impact on shared operation for aircraft...

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Radar detection of thunderstorm hazards for air traffic control volume II: radar systems

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
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