09:25 How much can spy balloons see?
The Chinese surveillance balloon shot down over the United States earlier this month set off a flurry of action with three more unknown objects taken down by the Air Force in the following weeks.
After initial worries all four objects were linked, US President Joe Biden later explained there was nothing to suggest they were linked to the Chinese Balloon or were even from outside of the United States.
China has denied the balloon was for anything else aside for for scientific purposes but the Americans are still firm in their belief it was part of a sprawling intelligence collection programme.
Debris from the balloon, including its payload, have been recovered and are being studied by the US military.
So what are spy balloons, how do they work, how much can they can see, and was the panic they caused justified?
Kathryn asks Iain Boyd, a professor of aerospace engineering sciences and the director of the Center for National Security Initiatives at the University of Colorado
Photo: AFP / Chase Doak
