All you need to know about radars, and how they function even with cloud cover

The origin of Radar and Radar evasion

May 14, 2019 06:39 pm | Updated 07:43 pm IST

An air traffic controller monitors a radar screen in the Berlin Aircraft Traffic Control Center at Tempelhof Central Airport.

An air traffic controller monitors a radar screen in the Berlin Aircraft Traffic Control Center at Tempelhof Central Airport.

Prime Minister Narendra Modi’s recent comment about how he gave the go-ahead for the Balakot airstrike despite bad weather as the clouds would enable Indian Air Force fighter jets to evade enemy radars, has raised a storm on social media. So, what is a radar and how does it function?

What is a radar?

Radar stands for radio detection and ranging. A radar typically has a magnetron, transmitter, receiver, and a screen. The magnetron generates radio waves which are released through an antenna in different directions at certain time intervals. If there is an object in the air, an aeroplane for instance, the radio waves hit it and bounce back, to be caught by the receiver of the radar. By mapping the reflected waves on a screen with a grid map, the aeroplane is displayed as a blip on the screen and its movement is shown as the radio waves strike it at intervals (Remember all the Hollywood action movies!). This is the basic principle of a radar.

Over the decades, there have been tremendous technological advancements in radars, making them highly sophisticated and powerful.

By virtue of being radio waves, radars can see through cloud cover, and during day and night. In fact, that is what they are meant to do. Imagine rough weather and overcast skies over a city, but commercial flights continue taking off and landing at the airport. This is because the Air Traffic Controllers (ATC) across the world depend on radars.

All ATCs have two radars -- primary and secondary. The primary is a classic radar based on the principle described above. The secondary radar identifies the details of the aircraft by communicating with the transponders on the aircraft.

Thus, radars enable continuous airport operations in cloudy conditions. And that goes for military radars as well, including those of Pakistan, which has an advanced military.

Origin of Radar

The origin of the radar goes back to World War II, when the first radar was demonstrated in Britain in 1935. By the time the war began, Britain had a chain of radars along its coast to detect intruders. And by the end of WW-II, all major countries involved deployed radars.

Ground based radars have limitations primarily due to the curvature of the earth. So radars were mounted on aircraft which fly thousands of feet above the ground with 360-degree coverage. These are known as Airborne Warning and Control System (AWACS), and are major force multipliers in today’s battlefields.

During the Balakot airstrike on February 26, IAF had fielded both indigenous and Israeli AWACS to direct the fighters jets on their strike mission and monitor the skies for any movement by Pakistani jets.

Radar evasion

Over the years, as radars have improved so have the technologies to evade them.

There are many ways of evading radars or reducing the radar cross section or foot print. That’s where the concept of stealth comes in. Stealth is a relative concept and not absolute.

Radars essentially identify an object by the reflected radio waves. So if the radio waves can be deflected away from the receiver, that reduces the footprint. A classic example for this is the US F-117 which is now out of service.

Another way is to absorb some or most of the radio waves with radar absorbent paint, and changing the shape to minimise the cross section. The iconic US B2 bomber is a perfect example for this.

The latest stealth planes F-22 and F-35 use a combination of these to evade radars.

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