The Luneburg lens as a radio telescope element

Serious consideration of the scientific objectives for the next generation decimeter radio telescope includes, as a major objective, the desire to study interstellar hydrogen in the early universe occurring at large red-shifts. This has led to the proposal for a Square Kilometre Array (SKA). Among the primary specifications are large collecting area (the square kilometre relates to the effective collecting area of the telescope at 1.4 GHz), wide frequency coverage (200 MHz to 2 GHz minimum), large dynamic range, full sky coverage and the possibility of forming multiple simultaneous beams on the sky. A lens can have both a wide field-of-view and a high aperture efficiency. Indeed, only a lens appears to offer the possibility of maintaining a constant collecting area for all viewing directions and thereby allowing a multiple beam capability through the use of a fixed focal plane array or lightweight movable feeds. We propose the consideration of a Luneburg lens to meet the requirements of the antenna element for the SKA.