New Aviation Radars Covering Tehran Skies

EghtesadOnline: Two strategic radar projects for Tehran’s sky, namely Monopulse Secondary Surveillance Radar and Primary Surveillance Radar, became operational in a ceremony on Sunday, at a radar site called "Kooshk Bazm" along Tehran-Qom Freeway.

News ID: ۷۴۷۹۳۶

22 July 2019

Minister of Roads and Urban Development Mohammad Eslami, the head of Iran Airports Company, Siavash Amir-Mokri, and other officials attended the ceremony.

The radars boast vast aviation features regarding communication systems, navigation aid, surveillance, safety and security, and help complete the coverage of Tehran’s terminal maneuvering area (TMA) and increase flights’ safety factors, IAC reported on its website, www.airport.ir.

The newly-installed systems will back radars at Mehrabad International Airport, Imam Khomeini International Airport and airports in Alborz, Qom and Qazvin provinces, Financial Tribune reported.

The installation of the radar systems took six months, which marks the second experience in Iran of such an installation. The first ones were previously installed at Bandar Abbas.

TMA is an aviation term to describe a designated area of controlled airspace surrounding a major airport where there is a high volume of traffic. Such an airspace is normally designed in a circular configuration centered on the geographic coordinates of the airport and differs from a control area in that it includes several levels of increasingly larger areas, creating an "upside-down wedding cake" shape.

Eslami noted that the installation of the radars is an important step toward increasing flight safety and expressed hope that Iran will be able to cover all the skies across the country.

Secondary surveillance radar (SSR) is a radar system used in air traffic control. Not only does it detect and measure the position of aircraft, i.e. bearing and distance, but also requests additional information from the aircraft itself, such as its identity and altitude.

Unlike primary radar systems that measure the bearing and distance of targets using the detected reflections of radio signals, SSR relies on targets equipped with a radar transponder that replies to each interrogation signal by transmitting a response containing encoded data.

Monopulse secondary surveillance radar (MSSR), Mode S, TCAS and ADS-B are similar modern methods of secondary surveillance.

According to SKYbrary, an electronic repository of safety knowledge related to flight operations, air traffic management and aviation safety in general, Monopulse Secondary Surveillance Radar is a technique developed to overcome two common problems with surveillance radar systems: one when several aircraft are in close proximity, or are located in the same direction, their transponder replies can overlap due to the finite size of the antenna beam width (typically 2-3 degrees).

When this happens, the ground decoder becomes confused and the information is lost. This problem is known as “Garbling”. The other is when many aircraft are in the vicinity, responses transmitted by some of these may be interpreted as being from the interrogated SSR, causing confusion and error. This problem is known as “Fruit”.

These problems are resolved by analyzing the received signals using a computer and by transmitting from the radar at a much reduced rate (about one-tenth of the previously used rate).

As a result, Garbling and Fruit are reduced by about 90% while directional accuracy is tripled compared to conventional SSR.

A Primary Surveillance Radar is a conventional radar sensor that illuminates a large portion of space with an electromagnetic wave and receives back the reflected waves from targets within that space. The term thus refers to a radar system used to detect and localize potentially non-cooperative targets.

PSR pertains to air traffic control and is opposed to the secondary radar that receives additional information from the target's transponder.