China's FAST telescope achieves domestic replacement of key component

China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is replacing a critical component with domestically produced technology for the first time, according to the National Astronomical Observatories of the Chinese Academy of Sciences.

The world's largest single-dish radio telescope is currently replacing six giant steel cables with a combined length of nearly 4,000 meters. Each cable weighs more than six tonnes, and the replacement work is expected to continue through late June.

The cables are used to support and control FAST's feed cabin, one of the telescope's core components. Suspended by six giant steel cables, the 30-tonne cabin can contract and rotate in coordination, allowing it to achieve ultra-precise positioning and tracking above the telescope's reflective surface.

Operating at a height of 140 meters and across a range of 206 meters, the feed cabin relies on the cables for real-time movement and positioning. Each cable endures hundreds of bending motions and pulse loads every day, placing extremely high demands on fatigue resistance. Engineers say the cables must remain free of wire breakage for at least five years to ensure efficient telescope operations.

Since FAST began operations in 2016, the telescope had relied on imported steel cables. A previous replacement was carried out in 2021.

To achieve domestic substitution and verify the performance of the new cables, the FAST team conducted extensive testing, including 62,000 repeated pulley operations and 200,000 pulse fatigue tests.

In August 2025, the newly developed domestic steel cables successfully passed three rounds of iterative experiments. Researchers said the breakthrough not only improves supply chain security, but also establishes a complete technological system covering materials, cable manufacturing, evaluation and testing, providing replicable experience for other major scientific infrastructure projects.

The six domestically produced steel cables have now arrived at the FAST site, with installation work expected to be completed by late June.