The Green Bank Telescope (GBT) is the world's largest fully mobile radio telescope. The surface area of the GBT is 100 by 110 meters with a separate actuator for each of the 2,004 surface panels. Infrared lasers are used to measure the position of each plate so that if one is to move even slightly out of place the actuator can move it back into it proper posistion, resulting in a surface that can be kept in an optimal state throughout an observation with the telescope. A laser alignment system also allows for precise knowledge of the posisitioning of the dish by utilizing reflectors in the mountains and around the base of the telescope itself.

External link

Official NRAO/Green Bank GBT Page