The US military shot down what US officials called a Chinese surveillance balloon off the coast of South Carolina on February 4, 2023. Officials said that the US Navy planned to salvage the rubblelying in shallow water.
The US and Canada tracked the balloon as it crossed the Aleutian Islands, flew over western Canada and entered US airspace via Idaho.
US Department of Defense officials confirmed on February 2, 2023 that the military was there track the balloon as it flew at an altitude of about 60,000 feet over the continental United States, including over Malmstrom Air Force Base in Montana. The base houses the 341st Missile Wing, which operates nuclear ICBMs.
The next day, Chinese officials confirmed that the balloon was theirs however, denied that it was intended for spying or to enter US airspace. US Secretary of State Antony Blinken said the balloon’s incursion led him to do so cancel his trip to Beijing. He was scheduled to meet with Chinese Foreign Minister Qin Gang on February 5-6.
The Pentagon has reported that a second suspected Chinese balloon was seen over Latin America. On February 4, officials told reporters that a third Chinese surveillance balloon was operational somewhere else in the world and that the balloons were there Part of a Chinese military surveillance program.
Surveillance of an enemy from a balloon dates back to 1794 when the French used a hot air balloon to track down Austrian and Dutch troops at the Battle of Fleurus.
We asked aerospace engineer Ian Boyd from the University of Colorado Boulder to explain how spy balloons work and why someone in the 21st century would use one.
What is a spy balloon?
A spy balloon is literally a gas-filled balloon that flies quite high in the sky, more or less where we fly commercial airliners.
It’s got some sophisticated cameras and imaging technology, and it’s pointing all of those instruments at the ground. It gathers information through photography and other depictions of everything that is going on on the ground below.
Why would anyone use a spy balloon instead of just using spy satellites?
Satellites are the preferred method of spying from above. Spy satellites are overhead today, usually one in two different types of orbits.
The first is called Low Earth Orbit, and as the name suggests, these satellites are relatively close to the ground. But they are still hundreds of miles above us.
When it comes to photographing and photographing, the closer you are to something, the clearer you can see it, and the same goes for espionage. The satellites that are in low earth orbit have the advantage of being closer to the earth, allowing them to see things more clearly than more distant satellites.
The disadvantage of these low-Earth satellites is that they are constantly moving around the Earth. It takes them about 90 minutes to orbit the earth. That turns out to be pretty quick when it comes to getting clear photos of what’s going on below.
The second type of satellite orbit is called geosynchronous orbit, and that’s a lot further away. It has the downside that it’s harder to see things clearly when you’re very, very far away. But they have the benefit of what we call persistence and allow satellites to take pictures continuously.
In these orbits, you’re basically looking at exactly the same piece of ground on Earth’s surface all the time, because the satellite is moving exactly as the Earth is rotating—it’s rotating at exactly the same speed.
A balloon gets the best of it in a way. These balloons are much, much closer to the ground than either of the satellites, allowing them to see even more clearly.
And then, of course, balloons move, but they move relatively slowly, so they also have some endurance. However, espionage is not typically done with balloons these days, as they are a relatively easy target and not fully controllable.
What types of surveillance are spy balloons capable of?
I don’t know what’s on that particular spy balloon, but it’s probably different types of cameras collecting different types of information.
Today, imaging is performed in different regions of the world electromagnetic spectrum. Humans see in a certain part of this spectrum, the visible spectrum. So if you have a camera and take a picture of your dog, that’s a viewable picture.
That’s one of the things spy planes do. They take photos regularly, although they have very good zooming skills to be able to enlarge what they see quite a bit.
But other types of information can also be gathered in other parts of the electromagnetic spectrum.
Another fairly well known one is infrared. If it’s night, a camera operating in the visible part of the spectrum won’t show you anything. It’s all getting dark. But an infrared camera can record things from heat in the dark.
How do these balloons navigate?
Most of these balloons literally go where the wind blows. There may be a bit of navigation, but there are certainly no people on board. You are at the mercy of any weather.
They sometimes have guiding devices on them that change a balloon’s altitude to catch winds in certain directions.
According to reports, US officials said the Chinese surveillance balloon had propellers to steer it. If confirmed, it means the operator would have much more control over the balloon’s path.
What are the limits of a nation’s airspace? At what altitude does it become space and everyone has the right to be there?
There is an internationally recognized limit called Karman line at 62 miles (100 kilometers) altitude. This balloon is well below, so absolutely, definitely in US airspace.
Which countries are known for using spy balloons?
The Pentagon has run programs over the last several decades studying what can be done with balloons that has not been possible in the past. Maybe they’re bigger, maybe they can penetrate higher into the atmosphere, making them harder to shoot down or disable. Maybe they could be more persistent.
The widespread interest in this incident illustrates its unusual nature. Few people would expect every country to actively use spy balloons nowadays.
The US flew many balloons over the Soviet Union in the 1940s and 1950s, and these were eventually replaced by the high-altitude spy planes U-2and they were later replaced by satellites.
I’m sure a number of countries around the world have regularly gone back to re-evaluate: are there other things we could do with balloons now that we couldn’t do before? Do they fill in some gaps that we have from satellites and airplanes?
What does that say about the nature of this balloon that China has confirmed is theirs?
China has been complaining for many years about US espionage on China by satellites, by ships. And China is also known for getting involved somewhat provocative behavior, as in the South China Sea, sailing close to other nations’ borders and saber-rattling. I think it falls into that category.
The balloon poses no real threat to the US, I think sometimes China is just experimenting to see how far they can push things. That’s not really very advanced technology. It serves no real military purpose. I think it’s much more likely some sort of political message.
This article was updated to include the news that the balloon was shot down by the US military.
Ian BoydProfessor of Aerospace Engineering, University of Colorado Boulder
This article is republished by The conversation under a Creative Commons license. read this original article.
