Publications

The ATC community is seeking a way to obtain aircraft ID and improved surveillance on the airport movement area. Surface radars provide good surveillance data, but do not provide ID, may not cover the whole movement area, and suffer from false reflection targets and performance degradations in rain. This report describes an evolutionary technique employing multilateration, TCAS technology, and existing ATCBI transponders to provide the desired surface surveillance information. Five multilateration receiver/transmitters (RTs) based on TCAS units, and a central multilateration computer processor were procured and installed on the highest available buildings on the perimeter of the north side of Atlanta's Hartsfield airport. The resulting coverage was such that there was a 93% probability that a multilateration position would be computed on a given Mode S short squitter emitted from a a target at a randomly selected position on the movement area. Multilateration was performed on ATCRBS targets using replies elicited by whisper shout methods originally developed for TCAS. Measurements showed that whisper shout was successful in degarbling targets that were in close proximity on the movement area. The probability of obtaining an ATCRBS multilateration position in a given one second interval depended on the number of whisper shout interrogations transmitted. The equipment required over 10 interrogations per target per second to obtain per second multilateration update rates on two typical targets of 58% and 83% respectively. This less than anticipated performance was primarily due to the inefficient whisper shout interrogation technique that was used in the test equipment. This can be corrected in next generation equipment. The multilateration accuracy was about 20 feet one sigma, as anticipated from theoretical considerations and previous experience with other equipment. By combining the multilateration data with ASDE data and tracking the results, it would be possible to obtain track reliabilities on the airport surface similar to that obtained elsewhere in the ATC system but update rates of 1Hz as required for surface surveillance and control purposes. The RTs were also capable of receiving Mode S long squitters containing GPS position information. The probability of at least one of the 5RTs receiving a given long squitter was essentially 100% on the movement area.

MIT Lincoln Laboratory, under sponsorship of the FAA, has installed a modified Raytheon pathfinder x-band marine radar at Logan Airport in Boston, Mass. and has developed a real- time surveillance system based on the pathfinder's digitized output. The surveillance system provides input to a safety logic system that will ultimately activate a set of runway status lights. This paper describes the portion of the surveillance system following the initial clutter- rejecting preprocessing, described elsewhere. The overall mechanism can be simply described as a temporal constant false alarm rate front end followed by binary morphological operations including connected components feeding a scan-to-scan tracker. However, a number of refinements have been added leading to a system which is close to being fieldable. Both the special difficulties and the current solutions are examined. The radar hardware as well as the computational environment are discussed. An overview of the clutter rejection preprocessing is given, as well as physical and processing related challenges associated with the data. Algorithmic description of the current system is presented and its real-time implementation outlined. Performance statistics and envisioned algorithmic improvements are presented.

To enhance safety and expedite aircraft traffic control at airports, the Federal Aviation Administration (FAA) is in the process of developing automation aids for controllers and pilots. These automation improvements depend on reliable surveillance of the airport traffic, in the form of computerized target reports for all aircraft. One means of surveillance of the airport is primary radar. A short range radar of this type is called airport surface detection equipment or (ASDE). Lincoln Laboratory is participating in this development program by testing a system of surveillance and automation aids at Logan International Airport in Boston, Mass. This work is sponsored by the FAA. This paper describes the radar equipment being used for surface surveillance at Logan Airport and the characteristics of the radar images it produces. Techniques for automatic tracking of this radar data are also described along with a summary of the tracking performance that has been achieved. Two companion papers in this session relate to this same radar surveillance and provide more in-depth descriptions of the radar processing.

Automation aids which increase the efficiency of the controller and enhance safety are being sought by the Federal Aviation Administration (FAA). This paper describes the target detection algorithms developed by the MIT Lincoln Laboratory as part of the airport surface traffic automation (ASTA) and runway surface safety light system (RSLS) programs sponsored by the FAA that were demonstrated at Logan International Airport in Boston, Mass. from September 1992 through December 1993. A companion paper to this conference describes the ASTA and RSLS system demonstration. Another companion paper describes the tracking algorithms. Real-time, parallel processing implementations of these surveillance algorithms are written in C++ on a Silicon Graphics Inc. Unix multiprocessor. The heavy reliance on commercial hardware, standard operating systems, object oriented design, and high-level computer languages allows a rapid transition from a research environment to a production environment.

An airborne traffic situation display system which could be used as an adjunct to the evolving National Airspace System/Automatic Radar Control Terminal System (NAS/ARTS) is described. In the proposed system, a contemporary realization of an old concept, the NAS/ARTS data are broadcast. A small digital computer in an aircraft then selects from the message stream the data on its own aircraft, nearby aircraft, and a local map. These data, plus aircraft heading data from a directional gyro, are used to generate a situation display that can be aircraft-centered and heading-oriented.

By the mid-1970's, the evolving NAS/ARTS ground environment will provide the air traffic controllers with high quality computer-processed traffic situation displays. We believe it would be useful, particularly in busy terminal areas, to display some of this data in the cockpit. Systems with this objective have been constructed and flight tested at least 3 times during the past 25 years, but these earlier systems could not benefit from: 1) a source of computer-processed data of the quality to be available from NAS/ARTS; 2) aircraft altitude information; 3) contemporary digital data link techniques; and 4) airborne equipment capable of automatically selecting and displaying only information relevant to a particular airplane. It is believed that an effective cockpit display would permit pilots, under IFR conditions, to retain some of the station-keeping and navigation functions they perform during VFR conditions and thereby improve the efficiency of terminal area operation. The goals of the proposed program are: a) to evaluate the effectiveness of this class of system in reducing pilot and controller work loads, and b) to determine its potential for expediting traffic flow in busy terminal areas. A simulated cockpit display has been developed and experienced pilots and controllers who have "flown" it have endorsed enthusiastically the desirability of evaluating this class of system in an operational environment.