SPY BALOONSChinese Spy Balloon Over the U.S.: An Aerospace Expert Explains How the Balloons Work and What They Can See

By Iain Boyd

Published 6 February 2023

Balloons are much closer to the ground than any satellites, so they can see even more clearly. And balloons are moving relatively slowly, so they also have a degree of persistence. However, spying is not usually done these days with balloons because they are a relatively easy target and are not completely controllable.

The U.S. military shot down what U.S. officials called a Chinese surveillance balloon off the coast of South Carolina on Feb. 4, 2023. Officials said that the U.S. Navy planned to recover the debris, which is in shallow water.

The U.S. and Canada tracked the balloon as it crossed the Aleutian Islands, passed over Western Canada and entered U.S. airspace over Idaho. Officials of the U.S. Department of Defense confirmed on Feb. 2, 2023, that the military was tracking the balloon as it flew over the continental U.S. at an altitude of about 60,000 feet, including over Malmstrom Air Force Base in Montana. The base houses the 341st Missile Wing, which operates nuclear intercontinental ballistic missiles.

The next day, Chinese officials acknowledged that the balloon was theirs but denied it was intended for spying or meant to enter U.S. airspace. U.S. Secretary of State Antony Blinken said that the balloon’s incursion led him to cancel his trip to Beijing. He had been scheduled to meet with Chinese Foreign Minister Qin Gang on Feb. 5 and 6.

The Pentagon has reported that a second suspected Chinese balloon was seen over Latin America. On Feb. 4, officials told reporters that a third Chinese surveillance balloon was operating somewhere else in the world, and that the balloons are part of a Chinese military surveillance program.

Monitoring an adversary from a balloon dates back to 1794, when the French used a hot air balloon to track Austrian and Dutch troops in the Battle of Fleurus. We asked aerospace engineer Iain Boyd of the University of Colorado Boulder to explain how spy balloons work and why anyone would use one in the 21st century.

What Is a Spy Balloon?
A spy balloon is literally a gas-filled balloon that is flying quite high in the sky, more or less where we fly commercial airplanes. It has some sophisticated cameras and imaging technology on it, and it’s pointing all of those instruments down at the ground. It’s collecting information through photography and other imaging of whatever is going on down on the ground below it.

Why Would Someone Want to Use a Spy Balloon Instead of Just Using Spy Satellites?
Satellites are the preferred method of spying from overhead. Spy satellites are above us today, typically at one of two different types of orbit.