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Secondary Surveillance Radar
Published in Habibur Rahman, Fundamental Principles of Radar, 2019
The rapid wartime development of radar had obvious applications for air traffic control (ATC) as a means of providing continuous surveillance of air traffic disposition. This type of radar, now called a primary radar, can detect and report the position of anything that reflects its transmitted radio signals. For air traffic control purposes this is both an advantage and a disadvantage. Its targets do not have to cooperate; they only have to be within its coverage and be able to reflect radio waves. It only indicates the position of the targets without proper identification. Primary radar is still used by ATC today as a backup/complementary system to secondary radar, although it has limited coverage and information.
The Systems Perspective in Air Transportation
Published in Steven J. Landry, Handbook of Human Factors in Air Transportation Systems, 2017
Surveillance infrastructure is the means to collect data on the location of all flights operating at an airport or in the airspace. There are several ways of collecting the location of each flight. A primary radar is a ground-based electronic system that transmits signals into the airspace and records when these signals are reflected back. The time for transmission and reflection determines the distance of the aircraft from the radar transmitter. Primary radar can only tell if an object is in the airspace, it cannot identify the object (e.g., flight number).
Estimation of aircraft distances using transponder signal strength information
Published in Cogent Engineering, 2018
Mode C interrogations are broadcast from both approach control and Air Route Traffic Control Center (ARTCC) radar installations. These interrogations, as the principal component of Secondary Surveillance Radar (SSR), are broadcast from antennas that are collocated with primary radar, which is used by air traffic control computers to determine the azimuth and range of aircraft within the facility’s designated airspace. The most common type of radar installation is ASR-9; 135 of these systems are currently deployed across the United States. The ASR-9 antenna has a rotational speed of 12.5 rpm and therefore requires 4.8 s for a 360° scan of its associated airspace. Because an aircraft may be interrogated by multiple SSR interrogators, dependent on position, the timing of Mode C replies generated by the aircraft is stochastic in nature. However, if one assumes that an aircraft is within range of a single SSR site, the expected frequency of Mode C replies is 0.208 Hz.
A New Efficient Array Architecture for Small L-Band Secondary Surveillance Radars with Reduced Number of Elements
Published in Electromagnetics, 2022
Sayed Hesamoddin Najmolhoda, Mohammad Ali Khak, Mehdi Shirichian, Amirreza Nikfal, Reza Bayderkhani, Hadi Aliakbarian
Tracking and identifying any operational aircraft are highly consequential in preventing collisions in the sky. This task, which is the role of Aviation Traffic Control (ATC) systems, is performed with the help of Secondary Surveillance Radars (SSR). In contrast with primary radar, the clutter effect in SSR is negligible because of obtaining replies on a different frequency from the interrogations (Stevens 1985). Also, extra information can be obtained from the responses of the aircraft to this system. Other advantages of SSRs are their long-range coverage and low average power level (Stevens 1988).