FAST does 'eye exercises' to maintain top performance By Yang Jun in Guiyang | chinadaily.com.cn | Updated: 2021-02-09 14:49 Share CLOSE The 500-meter Aperture Spherical Telescope under construction. It opened in 2016 in Pingtang county Guizhou province. [Photo by Dai Chuanfu/For chinadaily.com.cn] The 500-meter Aperture Spherical Telescope — known as FAST, the world's largest radio telescope in Pingtang county, Guizhou province — has been upgraded and maintained many times after making some great achievements. The so-called China's sky eye has a 250,000-square-meter "retina". With more than 2,200 hydraulic actuators acting as neurons to precisely control the "retina", how do engineers keep it healthy?