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Beacon radar and TCAS reply rates: airborne measurements in the 1090 MHz band

Published in:
MIT Lincoln Laboratory Report ATC-256

Summary

The Federal Aviation Administration (FAA) is in the process of developing Automatic Dependent Surveillance Broadcast (ADS-B) techniques. In one candidate system, GPS-Squitter, each aircraft periodically broadcasts messages, called "squitters," that report the aircraft's identification, position, and velocity. The position and velocity information may be obtained from the Global Positioning System (GPS) or some other navigation device. Reception of squitters can be used for several purposes, including surveillance of airborne aircraft by a ground station, surveillance of aircraft on the airport surface, and air-to-air surveillance... In developing the new system, it is necessary to know the rates of existing signal transmissions in the 1030 and 1090 MHz frequency bands, which are the beacon-radar and TCAS interrogation channels. The GPS-Squitter would be transmitted in the 1090 MHz band, like a reply. A key issue is the possibility of interference to squitter reception from existing signals in the 1090 MHz band....To validate these initial calculations, Lincoln Laboratory has made direct measurements of the rates of existing transmissions in both bands. These signals consist mainly of interrogations in the 1030 MHz band and replies in the 1090 MHz band. This report focuses on airborne measurements that have been made at 1090 MHz. (Not complete)
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Summary

The Federal Aviation Administration (FAA) is in the process of developing Automatic Dependent Surveillance Broadcast (ADS-B) techniques. In one candidate system, GPS-Squitter, each aircraft periodically broadcasts messages, called "squitters," that report the aircraft's identification, position, and velocity. The position and velocity information may be obtained from the Global Positioning System...

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Air Force planetary defense system: initial field test results

Published in:
Proc. of the Fifth Int. Conf. on Space '96: Engineering, Construction, and Operations in Space V, 1-6 June 1996, pp. 46-53.

Summary

Over the past several years, the Air Force has been developing new devices and technology for the detection and tracking of earth orbiting satellites. This technology has been targeted to provide an upgraded capability for an operational space surveillance system called GEODSS. Currently, a number of GEODSS systems are deployed around the world as part of the world-wide space surveillance system operated by the US Air Force. Each GEODSS site is currently equipped with 1-meter class telescopes and EBSICON detector systems which represent 1970's technology. The Air Force is now in the process of upgrading the GEODSS system to achieve the performance offered by state of the art detector systems. Under Air Force sponsorship, Lincoln Laboratory has developed a new generation of sensitive, large format, frame transfer CCD focal planes for GEODSS. These focal planes have been installed in a new generation of cameras and are currently undergoing testing at the Lincoln Laboratory Experimental Test Site (ETS). When equipped with the new focal plane and camera technology, the modest sized GEODSS telescopes have considerable capability to conduct large coverage, sensitive searches for earth crossing asteroids. Theoretical analysis has indicated that the CCD equipped GEODSS telescope will be capable of achieving a limiting magnitude of 22, over a 2 sq/deg field of view, with about 100 seconds of integration. This is comparable to the sensitivity of considerably larger telescopes equipped with current cameras. In addition to the high sensitivity, the CCD is configured for frame transfer operations which are well suited to asteroid search operations. This paper will present the results of the initial system tests conducted at the ETS and will discuss how this technology fits into a concept of operations for a planetary defense system based on the Air Force developed technology.
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Summary

Over the past several years, the Air Force has been developing new devices and technology for the detection and tracking of earth orbiting satellites. This technology has been targeted to provide an upgraded capability for an operational space surveillance system called GEODSS. Currently, a number of GEODSS systems are deployed...

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Beacon radar and TCAS interrogation rates: airborne measurements in the 1030 MHz band

Published in:
MIT Lincoln Laboratory Report ATC-239

Summary

Airborne measurements were made of the rates of beacon-radar interrogations and suppressions in the 1030 MHz band. These measurements were undertaken in order to provide a basis for interference analysis of the proposed system of GPS-Squitter. The measurements were made during a flight along the East Coast, including New York, Philadelphia, Baltimore, and Washington. Measurements were also made at Atlanta and in the Dallas Fort Worth area. Results were given in a form that shows the rates of interrogations and suppressions as a function of time and location of the aircraft. Interrogations are also separated into those that were transmitted by ground-based interrogators and those that were transmitted by airborne TCAS equipment. Mode S interrogations were also separated from other modes. The number of TCAS aircraft in the vicinity was also measured during the flights. The results indicate that the rates of interrogations and suppressions were consistent in most respects from location to location. The rates Mode A and C interrogations from the ground were consistently less than 100 per second with two brief exceptions. Previous measurements had indicated a trend of decreasing interrogation rates with time since the early 1970's. The new measurements support this observation and indicate that the trend has continued.
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Summary

Airborne measurements were made of the rates of beacon-radar interrogations and suppressions in the 1030 MHz band. These measurements were undertaken in order to provide a basis for interference analysis of the proposed system of GPS-Squitter. The measurements were made during a flight along the East Coast, including New York...

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GPS-squitter automatic dependent surveillance broadcast: flight testing in the Gulf of Mexico

Summary

During November - December 1994, MIT Lincoln Laboratory conducted a field evaluation of the air surveillance capabilities of GPS-Squitter in the Gulf of Mexico. Three squitter ground stations were located in the vincinity of Morgan City, Louisiana, for this evaluation: two were located on offshore oil platforms, and the third was located at an onshore heliport. Surveillance coverage tests were flown over the Gulf with three test aircraft - two helicopters and one Cessna 421 fixed wing aircraft. The helicopters flew at altitudes ranging from 100 to 2000 feet above sea level and the Cessna flew at 7500 and 20,000 feet. Extended squitter messages broadcast by each of the test aircraft provided aircraft position and identification. This report documents results of these texts and compares measured coverage to predicted coverage from the ground stations. Based on the good agreement between predicted and measured performance, a description of a possible operational system is included that would provide surveillance of the entire Gulf region serviced by oil platform helicopters. The report concludes that GPS Squitter is a near-term option for providing accurate, real time surveillance of aircraft operating in the offshore airspace in the Gulf of Mexico.
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Summary

During November - December 1994, MIT Lincoln Laboratory conducted a field evaluation of the air surveillance capabilities of GPS-Squitter in the Gulf of Mexico. Three squitter ground stations were located in the vincinity of Morgan City, Louisiana, for this evaluation: two were located on offshore oil platforms, and the third...

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Runway status light system demonstration at Logan Airport

Summary

The Runway Status Light System (RSLS), developed under the FAA's Airport Surface Traffic Automation (ASTA) program, is intended to help reduce the incidence of runway incursions and airport surface accidents. It will do so by providing a preventive, back-up system of automatically controlled lights on the airport surface that inform pilots when runways are unsafe for entry or takeoff, and by providing controllers with enhanced surface radar displays. This report documents a proof-of-concept evaluation of the RSLS at Boston's Logan Airport. It details the methods used to provide the necessary surface surveillance and safety logic to allow a computer to operate the runway status lights and associated controller displays without human assistance. The system was installed and tested off-line at Boston's Logan Airport using an inexpensive commercial marine radar as a primary surveillance source. The system operated live and in real time but the runway status lights were not physically installed. They were displayed on a scale model of Logan Airport located in a demonstration room that had a good view of the airport. This allowed visual comparison between the actual aircraft and the resulting lights and displays. In addition to providing a convincing demonstration of the system, real-timing viewing of the aircraft movement was an important aid in the development of the surveillance processing and safety logic software. Surveillance performance and runway status light operational performance were evaluated quantitatively. The probability of tracking an aircraft in movement areas with line-of-sight coverage was better than 98%. The false track rate was about four per hour, and the surveillance jitter was about 1 meter rms. From an operational point of view, had there been real lights on the field, it appears that they would have provided the intended safety back-up with little impact on airport capacity or controller and pilot workload, Only once in 15 minutes would the pilot population have observed a light in an incorrect state for more than four seconds. From the point of view of a specific cockpit crew, only once in 36 operations would a runway status light have been seen in an incorrect state for more than four seconds, and, furthermore, only once in 50 operations would light illuminations have interfered with normal, safe traffic flow. These are encouraging results for a system in an early demonstration phase because significant improvement is possible in all of these performance measures. Specific suggestions for improvement are included in this document.
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Summary

The Runway Status Light System (RSLS), developed under the FAA's Airport Surface Traffic Automation (ASTA) program, is intended to help reduce the incidence of runway incursions and airport surface accidents. It will do so by providing a preventive, back-up system of automatically controlled lights on the airport surface that inform...

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The ASR-9 Processor Augmentation Card (9-PAC)

Published in:
MIT Lincoln Laboratory Report ATC-232

Summary

Since 1990, the Airport Surveillance Radar-9 (ASR-9) has been commissioned and installed at more than 60 of the largest airports in the United States, and future installations are planned at more than 60 additional airports. After the first several systems were put into daily operation, air traffic controllers began to lodge complaints about the radar's performance. Problems included the detection of "phantom" aircraft caused by the reflection of beacon interrogation signals off buildings and other aircraft, the radar's losing track of targets during parallel approaches and departures, the inability to track highly maneuverable military aircraft through high-G turns, radar clutter caused by highways and weather, and system overloading as a result of signal returns from flocks of migrating birds. An initial investigation of the sources of these problems focused on the radar's post-processor. Nearly all of the problems could be addressed by additions to the post-processor software, but the post-processor was already running near capacity and there was no means for expansion. Thus, a new processor - the ASR-9 Processor Augmentation Card (9-PAC) - was designed to augment the existing system to allow for a significant increase in processing power. New algorithms were developed to run in 9-PAC to address the problems cited by the controllers.
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Summary

Since 1990, the Airport Surveillance Radar-9 (ASR-9) has been commissioned and installed at more than 60 of the largest airports in the United States, and future installations are planned at more than 60 additional airports. After the first several systems were put into daily operation, air traffic controllers began to...

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Data processing techniques for airport surveillance radar weather sensing

Published in:
Proc. IEEE 1995 Int. Radar Conf., 8-11 May 1995, pp. 521-528.

Summary

Discusses data processing techniques that can provide high quality, automated weather information using the FAA's existing Airport Surveillance Radars (ASR-9). The cost of modifying the ASR-9 is significantly less than that for deployment of the dedicated terminal Doppler weather radar. These techniques have been implemented on a prototype ASR-9 weather surveillance processor (WSP) and have been tested operationally at the Orlando, FL and Albuquerque, NM air traffic control towers. The key to the success of this system has been the development of innovative data processing techniques that accommodate the non-optimum parameters of the ASR as a weather sensor. The authors motivate the development of the ASR-9 WSP system and describe in detail the data processing techniques that have been employed to achieve an operationally useful capability. They provide an overview of the WSP and the ongoing system development and test program. They provide specifics on the data processing algorithms that have been key to successful implementation of this capability.
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Summary

Discusses data processing techniques that can provide high quality, automated weather information using the FAA's existing Airport Surveillance Radars (ASR-9). The cost of modifying the ASR-9 is significantly less than that for deployment of the dedicated terminal Doppler weather radar. These techniques have been implemented on a prototype ASR-9 weather...

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Automatic dependent surveillance broadcast via GPS-squitter: a major upgrade to the National Airspace System

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.
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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...

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TCAS III bearing error evaluation

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.
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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...

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GPS-squitter interference analysis

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.
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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...

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