"The VLBI Optics of the 40 meter CAY radiotelecope"
Authors: José Antonio López Fernández, Félix Tercero, Inmaculada Malo Gómez OAN
Abstract:
This paper presents the designed feed system for the new 40 meter radiotelescope for the OAN (National Astronomical Observatory from Spain). This radiotelescope will be use in astronomical and geodetic observations. It works in single dish and Very Long Baseline Interferometry (VLBI) observations to join to the European VLBI Network (EVN). This telescope is a Cassegrain-Nasmyth antenna and it is foreseed to cover the astronomical bands since 2 GHz up to 120 GHz. The receiver cabin will support up to ten receivers in two branches. The high frequency branch will be devoted to receivers from 45 GHz to 120 GHz. The paper focuses in the in the low frequency band, where the next receivers will be installed, 2 GHz, 3.3 GHz, 5 GHz, 8 GHz, 12 GHz, 22 GHz and 30 GHz. The receivers in S (2 GHz) and X (8 GHz) bands can be observed simultaneously. The elements of this beam wave guide system includes flat, elliptical, parabolical and dichroic mirrors, dielectric lenses and corrugated feedhorns. The optical design has been performed with Gaussian Beam Optics and Physical Optics with antenna efficiencies up to 80 %, low noise temperature and low crosspolarisation.