An overview of the Green Bank Telescope

The Green Bank Telescope (GBT) at the National Radio Astronomy Observatory (NRAO) site in Green Bank, is to be the largest, fully-steerable telescope in the world. The GBT has a main reflector 100 m/spl times/100 m with unblocked aperture. The telescope will operate at prime focus in the 230 MHz-1200 MHz frequency range and at Gregorian focus in the 1.15 GHz to >100 GHz range. The performance of the GBT above 15 GHz will be enhanced by the use of an active surface and a metrology system. The location of the surface panels are to be measured and adjusted to minimize the surface error as measured from a best-fit paraboloid. Switching between prime focus and secondary focus operation, as well as selection of different receivers, will be achieved in a few minutes giving the telescope a rapid frequency agility.