JIUQUAN – The Shenzhou XXIII crewed spaceship, set for launch on Sunday, has been adaptively improved with enhanced porthole protection against space debris, boosting its resilience to such threats, the China Manned Space Agency announced at a press conference on Saturday.

The improvement was made after the Shenzhou XX spaceship's return capsule viewport window suffered a suspected impact from space debris during its mission.

According to Zhang Jingbo, spokesperson of the agency, China's first-ever emergency launch mission in its manned space program history, carried out late last year, was completed within just 20 days, offering valuable practical experience for future missions.

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The three Shenzhou XX astronauts returned safely aboard the Shenzhou XXI spacecraft on Nov 14. On Nov 25, China launched the Shenzhou XXII spaceship to provide a return vessel for the three Shenzhou XXI astronauts, who are currently in orbit.

The return capsule of the Shenzhou XX spaceship, carrying no astronauts, touched down safely at a landing site in North China on Jan 19 this year.

Zhang said this mission fully validated the "rolling backup" strategy, with one combination of a spaceship and rocket assigned for launch and another combination designated as backup for each mission.

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Facing unexpected contingencies, resources were quickly mobilized, crew return and emergency launch plans formulated, and the astronauts successfully brought back while the backup spaceship docked with the space station, proving the strategy's effectiveness for long-term space station operations and offering a model for international emergency response, Zhang said.

The mission also provided a deeper understanding of space debris risks and orbital protection requirements, Zhang added.