Staff members tether a helium balloon to a targeted position as they test a microgravity mechanism in the maintenance of the reflector panels on the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in Pingtang County, southwest China's Guizhou Province, Aug. 30, 2019. Researchers with the China-based FAST, the world's largest single-dish radio telescope, on Friday tested a microgravity mechanism in the maintenance of the telescope's 4,450-panel reflector. The micro-G mechanism aims to help reduce the maintenance staff's body weight to a value within the reflector panels' range of durability using a helium-filled balloon 7.6 meters in diameter. (Xinhua/Ou Dongqu)