Development of a dual-reflector feed for the Arecibo radio telescope: an overview

The 305-m spherical-reflector antenna of the Arecibo Observatory will be equipped with a dual-reflector feed. This reflector system is often referred to as the Gregorian. An overview of the work that led to this design is given, and the basic ideas behind the design are described. The methods and algorithms that have been developed to synthesize the shapes of the two reflectors and to analyze them are reviewed. Results are given of analysis by forward ray tracing, using geometrical optics with edge-diffraction corrections included. At low frequencies, analysis is performed by physical optics (PO) integration. A ´mini-Gregorian´ that has been constructed, built, and tested to verify the dual-reflector feed concept is described.<>