A Chinese space station known as Tiangong-1 made an uncontrolled re-entry into Earth’s atmosphere on Sunday, breaking up over the Pacific Ocean and mostly burning up during descent.

Tiangong-1 was launched in 2011 as China’s first manned space station. In March 2016, the Chinese declared they had lost the ability to communicate with the spacecraft, leading to Sunday’s uncontrolled re-entry campaign.

The Department of Defense confirmed Tiangong-1 reentered the Earth’s atmosphere over the southern Pacific Ocean at approximately 5:16 p.m. (PST) on April 1, according to a press release from U.S. Strategic Command’s Joint Force Space Component Command. DoD relied on its Space Surveillance Network, which includes sensors and optical radars, to track the space station.

“One of our missions, which we remain focused on, is to monitor space and the tens of thousands of pieces of debris that congest it, while at the same time working with allies and partners to enhance spaceflight safety and increase transparency in the space domain,” Maj. Gen. Stephen Whiting, deputy commander of the space component and head of the 14th Air Force, said in the release.

Tiangong-1’s demise was also carefully recorded by researchers at the Aerospace Corporation, seeking to gain valuable information from the 9-ton spacecraft as it hurtled towards Earth. The Air Force relies heavily on analyses performed by the Aerospace Corp., a federally funded not-for-profit research center that provides engineering advice on the service’s space programs.

One reason Aerospace researchers were watching Tiangong-1 so closely Sunday is to improve prediction models. Each re-entry event offers Aerospace researchers more data for their ever-evolving models of the upper atmosphere of the Earth. Tiangong-1 was the first space station to re-enter Earth’s atmosphere since Russia’s Mir station returned in 2001, making it a particularly noteworthy event. These prediction models allow researchers to help inform decision makers when objects approaching Earth are potentially hazardous.

“I currently use at least six different mathematical models that try to predict where a space-object will be in the future,” said Andrew Abraham of Aerospace’s Systems Analysis and Simulation team. “That includes objects that are about to re-enter.”

Researchers also study spacecraft re-entries to help improve spacecraft designs. The Inter-Agency Space Debris Coordination Committee, which lays out guidelines to prevent the problem of space debris proliferation, encourages space companies to design for the spacecraft’s demise.

The Aerospace Corporation closely studies how spacecraft designs change during reentries and conducts lab tests on recovered space debris to improve their understanding of heating and material failure. Typically, 10 percent to 40 percent of the mass of a space object survives an atmospheric entry, according to researchers at Aerospace Corporation.

Tiangong-1 is far from the largest spacecraft to re-enter the Earth’s atmosphere. The largest re-entry was Russia’s Mir space station, with a mass of over 15 Tiangong-1s, but the Russians maintained control over it for a targeted re-entry over the Pacific Ocean in 2001. It is a best practice for operators of large space objects to perform a targeted entry at the end of life to safely dispose of spacecraft, Abraham said.

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