Ground Radar in Air Traffic Surveillance

062-03-02Pablo Asensio Martínez2026-04-012 min

Primary Surveillance Radar (PSR)

The PSR (Primary Surveillance Radar) is the most basic type of radar used on the ground for air traffic control.

Operating Principle

It works by emitting pulses of electromagnetic energy from a rotating antenna and detecting the echoes reflected by objects (aircraft, clouds, terrain).

  • Information Provided: It provides only 2D position:
    • Range: Calculated by measuring the time it takes for the pulse to travel back and forth (based on the speed of light). It is a slant range.
    • Bearing: Determined by the azimuth of the antenna at the moment the echo is received.
  • Limitations:
    • Does not provide altitude.
    • Does not identify the aircraft (no codes or registration).
    • Can be affected by weather (rain, clouds) and terrain (clutter).

Surface Movement Radar (SMR/ASMR)

The ASMR (Airport Surface Movement Radar) or ASMI (Airfield Surface Movement Indicator) is a short-range radar designed to monitor traffic on the airport ground.

  • Function: To provide controllers with a clear and detailed picture of all aircraft and vehicles on runways and taxiways, especially useful in low visibility conditions.
  • Characteristics:
    • High Definition: Requires very high resolution to distinguish close objects.
    • High Frequency: Operates at very high frequencies (SHF or EHF bands) to achieve the necessary resolution with reasonably sized antennas.
    • Size Detection: In older analog systems, high definition allowed estimating aircraft size by the size of the echo on the screen.
  • Modern Systems: Integrated with transponder data (multilateration) to tag targets with identification, improving safety and efficiency (A-SMGCS).

ATS Information Requirements

To provide ATS surveillance service, the minimum required information is:

  1. Position (provided by PSR or SSR).
  2. Map Information (airspace structure reference).

If SSR (Secondary Radar) is available, it adds:

  • Mode A: 2D Position + Identification Code (Squawk).
  • Mode C: 3D Position (adds pressure altitude).
  • Mode S: Additional data and selective data link.