reen ank elescope: the world's largest fully steerable single-dish radio telescope, under construction at the NRAO's facility in Green Bank, West Virginia. The GBT has a unique off-axis design intended to reduce sidelobe responses, and is due to be completed in 1997.

Gas bubble trauma. Fatal or sublethal fish syndrome resulting from exposure to high levels of dissolved gas in the water.

Gravity Belt Thickener. Process for thickening WAS that uses a fine mesh belt to separate solids and liquids by gravity. Liquid drops through the belt and is returned to the wastewater plant's liquid treatment processes, and thickened solids are collected for additional treatment or disposal.

Group on Basic Telecommunications