The Interrogator system also called Secondary Surveillance Radar (SSR) in civil application plays a vital role in the Air Defence system of a country. In an emerging complex security environment, timely and accurate identification of all targets – friendly and hostile as well as locating threat targets – is of paramount importance. This can be achieved with the help of Interrogator system
The system consists of two sub-systems, namely the Interrogator and a Transponder. It operates as per the recommendations of Annexure 10 of International Civil Aviation Organisation (ICAO) and STANAG 4193. SSR Interrogator operates in conjunction with a compatible Transponder that is fitted on the target aircraft. The airborne interrogator transmits pulsed signal with suitable spacing as per the desired mode of interrogation in a specified direction. Aircraft fitted with compatible transponder receives the interrogation signal and replies back in the form of another coded signal. These coded replies are received by the interrogator and processed for identification. It differentiates between friendly and enemy targets, by comparing the response received from the interrogated target with its own database
It provides additional target details such as height, range and azimuth. In addition, it can extract the target status like Communication Failure, Emergency and Hijack. Operation in mode – '4' enhances its capability to be secured, jam resistant and resistant to spoofing. Mode S or mode “select”, is a way to interrogate an airframe by using a distinct address, such as an aircraft address, that only a particular airframe will respond. The IFF Interrogator system consists of E-Scan or M-Scan Antenna Array, Transmitter, Receiver and Signal processor.