Following the recommendation of the Kargil Review Committee, the IAF had purchased two aerostats — also known as the Tethered Aerostat Radar System or TARS — for surveillance at a cost of over Rs 300 crore in 2007

Sources in the defence and security establishment said that while the balloon itself was American, there was a lot of Israeli equipment on board.

Aerostats are fitted with long-range radars, signal intelligence systems and meteorological instruments, among others. While military radars do have the ability to operate at long distances, being high in the air allows them to beat the limitations of the Earth’s curvature and other surface blocks.

The aerostat has the ability to pick up all take-offs and landings or large-scale military movements within a range of 100-600 km, depending on the kind of equipment on board and weather conditions.

“The aerostat operations are limited by weather conditions. For example, if the weather is bad, it has to be brought down. If there is cloud or smog, the radars don’t work effectively. The response of the aerostats has been mixed,” a source said.

Sources explained that the IAF wanted to purchase more aerostats but eventually gave up the idea, and that the issue has moved much further down in its list of priorities.

“When the IAF had got it first, it was an excellent system for surveillance” the source said.

The IAF feels that the answer to continuous surveillance is more airborne early warning and control aircraft (AWACS).

“AWACS is not weather dependent and can be deployed any time. It is able to move rather than remain stationary in one location,” a second source said.

Sources said the IAF has been upgrading the equipment on board the aerostat from time to time and is looking at indigenous systems.

Wind Factors Going Against India

The wind conditions are not favourable for India to deploy spy balloons, one of the sources said, explaining that the wind in this region is from west to the east, i.e. from Pakistan towards India. This means that while Pakistan can deploy such a balloon, it is not feasible for India.

Similarly, China also cannot deploy spy balloons targeting India unless they are operated from Pakistan.

However, despite the Chinese claims that it was the wind that took their balloon over American territory, Forbes reports that atmospheric modeling and smart algorithms allow a balloon to change altitude to catch wind in any desired direction, and even to circle around a given point on the ground.

The U.S. military has been carrying out trials of similar balloons for years. Not only did algorithms allow a balloon to stay within in a 30 mile circle by 2018, there has been a steady improvement as well.

US National Security Council spokesman John Kirby has said that the Chinese balloon was not merely drifting but had propellers and steering to give it a measure of control, even as it was swept along in the high-altitude jet stream winds. Thus, there’s a lot of technology that goes into these balloons, which rely on much more than just wind for navigation.