Noise reduction shield on a double-offset reflector antenna and its effect on antenna sidelobe structure

The Green Bank Telescope (GET) which is under construction at the Associated Universities, Inc./National Radio Astronomy Observatory (AUI/NRAO) site in Green Bank, WV. The telescope uses a double-offset geometry providing an aperture free of any blockage. The main reflector has a projected aperture of 100 meters in diameter. The subreflector is an ellipsoid of 7.5 meters in diameter. The telescope will operate from secondary focus at frequencies of 1.15 GHz and higher and will provide continuous coverage from 290 to 1230 MHz from prime focus. A study has been undertaken to install shields that will block the support arm structure and direct the spillover energy into the main reflector. This will alter the sidelobe structure in a controlled manner.