A Chinese surveillance balloon may have been a rude shock to the United States, but satellite photos reveal India is constantly under their watchful eye.

Balloons are being used to hoist radars, electronic eavesdropping and reconnaissance equipment high above the Himalayas as cheap, perpetual surveillance of Indian territory. And the high altitudes they obtain give such equipment enormous line-of-sight.

But they’re not ideal spy platforms, says Center for Strategic & International Studies (CSIS) strategic technologies director James Lewis.

“They are big and hard to hide,” he states. “They go where the winds take them [prevailing winds goes from North Asia to the Northwest United States] and are essentially unsteerable.”

A large balloon drifts above the Kingstown, N.C. area, with an airplane and its contrail seen below it. Photo / Brian Branch via AP

But Brian Barritt, chief technical officer of Google spin-off Aalyria, says balloon technology has moved on. His company is examining the feasibility of “atmospheric satellites” as communications relays.

“In our team’s work on Loon, we demonstrated the ability to navigate them autonomously using AI, to ‘station keep’ over designated area.”

Retired Indian Armed Forces Colonel Vinayak Bhat says a balloon similar to that observed over the United States was recently seen over Port Blair in the Andaman and Nicobar Islands, an Indian territory in the Bay of Bengal.

He was also instrumental in revealing the presence of large but traditional Tethered Aerostat Radar Systems (TARS) being caught by satellites operating from within the occupied territory of Tibet. Much of the mountainous border between it and India is disputed.

Indian news service The Print reported Beijing had bought several tethered surveillance balloons from Moscow in 2011. These radar stations could reach heights of 5000km.

It adds China has since moved on to build its own aerostats (tethered balloons) and mobile airships. One such aerostat, designated HBNST-KT-02, is estimated as being about 100m in length and 30m wide and capable of carrying a two-tonne cargo up to 7000m.

But a gargantuan hangar photographed deep inside a secretive Xinjiang desert reveals the full scope of China’s balloon plans.

Photos of China’s aerostats in the Xinjang desert. Images / Google Earth via Col. Vinayak Bhat

The 350 metres by 140 metres structure was completed in 2015. It can inflate and launch controlled-flight stratospheric airships that dwarf the balloon seen over the United States.

Such stratospheric balloons require advanced and expensive materials in the gas sack’s walls and cargo pods. This is because of the need for minimal weight and maximum resilience against temperature and pressure extremes. They’re also likely to be filled with increasingly rare helium to avoid the explosive potential of hydrogen.

A lot of hot air?

“Balloons would be a strange choice for a technologically advanced and sophisticated opponent,” says Lewis. “Since the balloon will never return to base, there has to be some way to transfer the collected data back home.”

And that, he says, means the balloon must transmit its data.

“The balloon could radio back any collected data, perhaps even to a Chinese satellite overhead, but there have been no reports of radio transmission from the balloon. Collecting data but being unable to get it back is a waste of time and money. No signal, no payload, no spying.”

Meanwhile, Chinese spy satellites pass over the US every day.

“China launched another four modern spy satellites last year,” the CSIS analyst adds.

Instead, Lewis believes the balloon is what China says it is – a weather balloon. “It’s embarrassing for China, and some Chinese meteorologist may be packing his or her bags for reassignment to Inner Mongolia”.

But the use of balloons may have advantages over satellites.

A satellite image of bomber aircraft at Engels Air Base in Saratov, Russia. Photo / Maxar Technologies via AP

In particular, they fly below the ionosphere. And that eliminates a significant source of interference when monitoring a broad spectrum of electronic emissions from electronic equipment below.

Barritt says the “mental model” most people have about such balloons is wrong.

“In reality, these high-altitude platforms can be quite capable; the phrase ‘atmospheric satellite’ would probably invoke a more accurate mental model.”

They can fly at three times the height of commercial airliners. And they can stay aloft indefinitely if powered by large solar arrays.

“They can support kilowatts of power to onboard communications or reconnaissance payloads,” Barritt says.

But Lewis argues much of Washington’s response has been an overreaction.

“Chinese spying is aggressive, and the United States needs a tougher response, but worrying about balloons is the equivalent of looking under the bed every night for Chinese spies,” he concludes.

- Jamie Seidel, news.com.au