The balloon panic comes with an asterisk, especially when it comes to China and America surveilling one another: both countries have spy satellites with comparable resolution. So it's no surprise that the Department of Defense can credibly say it tracked the balloon (Chinese, size of bus) from not long after it was launched.
The tracking of the balloon was first reported by The Washington Post.
China has insisted the balloon was for weather purposes and that it veered off course. A State Department official said in a statement last week that the balloon contained equipment that was "clearly for intelligence surveillance," including "multiple antennas" that were "likely capable of collecting and geo-locating communications."