The U.S. military embarked Monday on an underwater mission to collect remnants of the downed Chinese spy balloon, which Biden Administration officials hope will provide clues on how the Chinese government was carrying out a years-long surveillance operation.
The high-altitude spy balloons briefly flew over the continental U.S. at least three times over the past six years, but went undetected until the most recent one entered American airspace last week. “I will tell you that we did not detect those threats,” General Glen VanHerck, commander of U.S. Northern Command and the North American Aerospace Defense Command (NORAD) told reporters Monday. “And that’s a domain awareness gap that we have to figure out.”
The Pentagon hopes that new information about China’s surveillance practices will be collected from the operation to salvage the balloon that U.S. fighter jets shot down over the weekend off the Carolina coast. The military has “collected the majority of that debris” floating on the surface of the Atlantic Ocean, VanHerck said, adding that U.S. Navy search teams are now concentrating on an area under the water stretching 15 football fields by 15 football fields for bits of the surveillance apparatus that hung under the balloon. The debris field is scattered in less than 50 feet of water, but weather conditions prevented undersea collection until Monday morning.
At around 10 a.m. Monday, sailors set out to deploy underwater drones carrying side-scan sonar arrays, which are designed to create detailed imagery of what lies beneath the sea. Meanwhile, the oceanographic survey ship USS Pathfinder worked to map out the sea-bottom topography with its high-powered sonar equipment.
Read more: How an Alleged Spy Balloon Derailed an Important U.S.-China Meeting
The Chinese aircraft was huge, so there’s a lot to look for. The inflated balloon alone was assessed to be 200 feet tall, with a payload underneath it that’s comparable in size to a “regional jet,” VanHerck said. “Picture yourself with large debris weighing hundreds, if not thousands, of pounds falling out of the sky.”
The recovery is complicated by the potential presence of hazardous materials in the balloon, such as materials required for batteries or possible explosives. The FBI is assisting in the salvage operation “under counterintelligence authorities,” VanHerck said.
White House National Security Spokesman John Kirby said Monday that the recovery efforts will aim to sort out whether China had surveillance capability aboard the balloon beyond what the U.S. ascertained while observing its four-day flight over the country. “The time that we had to study this balloon over the course of a few days last week, we believe, was important and will give us a lot more clarity not only on the capabilities that these balloons have, but with what China is trying to do with them,” he told reporters.
Armed with the new intelligence, Kirby said the Biden Administration discovered “at least three” prior occasions where Chinese surveillance balloons traversed through U.S. air space. Two of those overflights took place during the Trump Administration, so the White House is preparing to brief key Trump officials on forensics.
Previous flights were shorter in duration, U.S. officials said. But the fact that a foreign aircraft was able to penetrate U.S. defense systems is alarming. The U.S. has spent decades investing billions of dollars into radar installations, satellite constellations, and other globe-spanning systems with the goal of detecting airborne threats.
How a giant balloon evades this dragnet has become a political flashpoint. “This Administration didn’t just fail here; they failed to prepare after the first time this happened” Representative Mike Turner of Ohio, the Republican chairman of the House Intelligence Committee, said Sunday on NBC’s “Meet the Press.”
The Chinese balloon traveled above the Aleutian Islands near Alaska on Jan. 28, then through Canada two days later, and ultimately into the continental U.S. over Idaho on Jan. 31, U.S. officials said. It became national news Feb. 2 after civilian pilots grew alarmed by its presence and the Pentagon admitted the alleged spy balloon was inside the country.
Biden asked the Pentagon to come up with options the day it entered the northern United States, a senior defense official told reporters. The military initially considered shooting down the balloon on Wednesday as it traveled over Montana. The state is home to Malmstrom Air Force Base, one of three bases that hosts nuclear-tipped intercontinental ballistic missile fields. But military commanders recommended against attempting a shoot-down out of fears that such an act could create falling debris that endangered people on the ground, the official said.
As the aircraft meandered over the central U.S., the Chinese government confirmed that the balloon was theirs but insisted it was merely a “civilian airship” used for weather research that accidentally entered U.S. airspace. The White House dismissed this depiction, pointing to the fact the balloon had propellers and rudders enabling it to speed up, slow down, loiter and alter its direction—though its maneuverability was impacted by the jet stream.
Read more: The Chinese Balloon Looks Nothing Like a Weather Balloon, Experts Say
On the orders of the President, an F-22 stealth fighter jet flew to an altitude of around 58,000 feet off the South Carolina coast on Saturday and shot down the balloon, which was floating less than 10,000 feet above it.
The Biden Administration has insisted the balloon doesn’t give China any additional surveillance capabilities beyond what’s aboard its spy satellites already orbiting the Earth. While the balloon’s ability to linger over specific sites does distinguish it from spacecraft, the U.S. military says it took every precaution to ensure any sensitive installations were safeguarded against the Chinese attempts to collect intelligence. It did not provide details.
For now, the Administration hopes it can glean new insights on this years-long Chinese operation and discover what secrets were lost—or which ones might’ve been—by obtaining and analyzing the wreckage currently strewn across the shallows in the Atlantic.
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Write to W.J. Hennigan at william.hennigan@time.com