Rural Montanans were the first civilians to report the Chinese spy balloon; why are such balloons still used?

One of Larry Mayer's photos for the Gazette

Rural Americans were the first civilians to spy China's "weather balloon" escapade. "The president of the United States knew about the presence of the Chinese spy balloon for several days before it was spotted drifting over Montana. But the White House wanted to keep it secret fearing news of the surveillance balloon would sabotage Secretary of State Antony Blinken’s planned diplomatic trip to China, Bloomberg News reported. . .That changed when on Feb. 1 when Billings Gazette photographer Larry Mayer, responding to vague reports that the airspace around Billings had been closed, photographed an odd glowing orb high in the sky," the Gazette reports.

"Using a large telephoto lens, Mayer discovered it was a high-altitude balloon powered by a large solar array. ... The Gazette’s publication of those photos, connecting them to the closed airspace and the fighter jets being scrambled to track the balloon, was quickly picked up by other media around the world — and the White House," the Gazette notes. "The White House was especially alarmed the balloon was hovering over a part of Montana that houses intercontinental nuclear missile silos."

Thank you, curious Montanans. So, what is a spy balloon? "A spy balloon is literally a gas-filled balloon that is flying quite high in the sky . . . 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," reports Iain Boyd of The Conversation, an independent source of news and views from the academic and research community.

How and why do spy balloons work? Spying satellites give us clues, but have built-in disadvantages. In low Earth orbit, Boyd writes, "It takes them about 90 minutes to do one orbit around the Earth. That's pretty fast to take clear photographs." In geosynchronous orbit, satellites stay in one place above the ground to capture images continuously but are much farther away. "A balloon in some ways gets the best of those. These balloons are much, much closer to the ground than satellites, so they can see even more clearly. The balloons are moving, but they’re moving relatively slowly, so they also have a degree of persistence."

What was it doing up there? "It’s likely to be different kinds of cameras collecting different types of information," Boyd writes. "The broad interest in this incident illustrates its unusual nature. Few people would expect any country to be actively using spy balloons these days." UPDATE: The Washington Post reports that the balloon is part of "a vast aerial surveilance program" that "has for years collected information on military assets in several countries, U.S. officials said."