China's FAST telescope, the world's largest single-dish radio telescope, requires a radio silence zone to avoid interference, impacting thousands of residents.
FAST telescope's location and size
The FAST telescope, known as the Five-hundred-meter Aperture Spherical Telescope, measures 500 meters in diameter and is located in a karst basin in Guizhou, China, since 2016. It occupies a natural depression called Dawodang in the Pingtang district.Radio silence requirements
The site requires a radio silence zone, with all electronic devices prohibited within a 5-kilometer radius. This restriction is due to the telescope's high sensitivity, which makes it vulnerable to interference from devices such as microwave ovens, smartphones, Wi-Fi, and garage remote controls.Relocation efforts for radio silence
To create this radio silence sanctuary, more than 9,000 people were relocated. The Guizhou government established an electromagnetic silence protection regulation covering a radius of 30 kilometers around the telescope.Zoning around the telescope
The area is divided into three zones: a core zone within 5 kilometers where radio emissions are prohibited, an intermediate zone from 5 to 10 kilometers, and a distant zone from 10 to 30 kilometers. The intermediate zone targets radio stations operating between 68 and 3,000 MHz, though specific power thresholds are not detailed.Human cost and public access
The human cost of this radio silence is significant, with more than 9,000 residents relocating, enough to fill a small city. Families within 5 kilometers received financial compensation to relocate elsewhere. Despite the restrictions, the site is not closed to the public.Tourism and scientific interest
Hundreds of thousands of visitors have visited since the observatory's opening, and Guizhou sees this as a way to develop scientific tourism. The telescope became the world's largest single-dish radio telescope when it began observations in September 2016.Mechanical design and capabilities
Its receiving surface is equivalent to 30 football fields. Unlike traditional telescopes, the structure itself does not move; instead, an active surface of 4,500 metal panels forms a mobile parabola on a lit circle with a diameter of 300 meters.Operational status and discoveries
A cabin where the waves are focused is suspended by 6 cables, about 140 meters from the panels. This mechanical system allows the telescope to observe sources up to 40 degrees from the zenith. The telescope was declared fully operational in January 2020 and officially opened to the global scientific community in 2021.Scientific achievements
By the end of 2019, it had identified 132 pulsar candidates, 93 of which were confirmed as new discoveries. These neutron stars could one day serve as reference points for spacecraft navigation. However, local radio silence does not solve all issues, as emissions from artificial satellites and powerful signals outside the zone remain detectable.Cultural significance and name
The detection of interference remains a research project in its own right, including for FAST. The site is known in China as the eye of the sky, or Tianyan.
