urn:nasa:pds:context:telescope:gbo.gbt_100m 1.0 1.16.0.0 Product_Context 2021-04-09 1.0 Initial version. urn:nasa:pds:context:facility:observatory.gbo telescope_to_facility 100 The Robert C. Byrd Green Bank Telescope (GBT) is located in Green Bank, West Virginia. The GBT is a parabolic dish covering 2.3 acres. The GBT has the largest collecting area of any fully-steerable telescope in the world. From the base to the top of its huge feed arm, the GBT stands 485 feet tall. Its 100-meter by 110-meter dish required 7,652 beams to support it on top of a nearly hemispherical tilting gear. A gigantic yoke cradles that gear above a base of concrete sunk 25 feet down to solid Appalachian bedrock. Over 17 million pounds of telescope glide around its 360-degree concrete track, thanks to four four-wheeled trucks, making the GBT the largest moving object on land. Its remarkable agility allows it to see 85% of the skies surrounding the Earth over the course of a year. Its 200-foot feed arm is a two-towered trusswork sticking out of the side of the dish and ending in a secondary mirror perched 60 feet above the dish. The secondary aims the dish's focused radio waves into one of eight receivers hanging in a rotating turret. On the fly, a new receiver can be spun into the beam to change the frequency being recorded. A ninth receiver can swing out on a boom arm in place of the secondary, giving astronomers a huge range of science they can pursue with one telescope. Scientists from around the world use the GBT to observe the skies for 6500 hours every year. The GBT's gigantic, unobstructed dish provides scientists with sensitive eyes on the faintest radio objects in the Universe.