Final checks

GUIZHOU, CHINA, 9 JANUARY

China’s Five-hundred-meter Aperture Spherical Telescope, or FAST, is the world’s largest and most sensitive radio telescope. Though it saw its first light in September 2016, the enormous telescope was only declared fully operational on 11 January 2020.

In this picture, a worker studies the reflector panels at the end of its three-year trial period, just two days before FAST began observations.

With such a gargantuan dish, focusing the telescope isn’t easy. Even the few millimetres that gravity pulls it out of shape can be enough to blur an image. To get around this, the dish is made up of individual metal panels that can be moved independently to adjust the focus.