Some problems associated with radar

One of the problems associated with radar is the amount of unwanted clutter (1) on the radar scope which the scanner picks up. This unwanted clutter is mainly echoes of stationary objects, such as mountains and other elevated terrain, as well as other objects situated close to the transmitting/receiving antennae.

With too much clutter, a controller cannot always see the aircraft. MTI (2) allows him to reduce such clutter. The MTI does this by not allowing echoes received from stationary objects to be displayed on the radar scope. A controller has an MTI switch at his console and with this he can control, to a degree, the amount of clutter caused by stationary objects.

However, clutter is not caused by stationary objects only, echoes received from precipitation and/or clouds also cause clutter. MTI is effective in removing clutter caused by precipitation and clouds to a limited extent since MTI permits any echo which is moving to be displayed. So an additional technique known as Circular Polarization (3) has been developed which prevents the display of most of the clutter caused by precipitation and clouds.

While using Circular Polarization, however, controllers would not be aware of the existence of any weather lying ahead of the aircraft, since all echoes from precipitation and clouds would be removed from his scope. Because of this, he could conceivably vector a pilot into turbulent or hazardous (4) meteorological conditions.

A solution to this problem has been to show on the scope the actual weather in the area. This clutter can be switched on and off. Another solution is to feed the weather information into the automaticdataprocessing (5) equipment for incorporation into the controller's computer processed radar scope. This information appears in digital form on the radar scope.

In most radar equipment, the controller is provided with the capability of using MTI alone, MTI plus Circular Polarization, or Circular Polarization alone, thus allowing him a considerable amount of flexibility. (6)

Besides the problems caused by clutter, the slashes (7) on the SSR scope, if too large, could overlap (8) with other slashes making it difficult to distinguish individual aircraft. To keep large slashes apart would require the controller to provide extensive separation between aircraft with resulting delays. This too is improved somewhat with the help of radar automation.

Although most of the deficiencies (9) in radar are characteristic of radar technology, improvements are constantly being made which will assist the air traffic controllers in the future.