Design of offset reflector with elliptical flat scan mirror and its applications to a dual-frequency, dual-polarization airborne rain radar observations

This paper presents the analysis, design, and development of a dual-frequency (Ku and Ka-band), and dual-polarization at each frequency, airborne rain radar antenna (ARRA) system. JPL is currently developing an airborne rain radar instrument to make such observations from NASA´s DC-8 aircraft. The antenna system uses a highly reflective elliptical scan mirror in conjunction with an offset parabolic reflector illuminated by a common-aperture feed system, consisting of a corrugated horn with four input ports. The reflecting mirror is rotated in azimuth to scan the antenna beam in the cross-track direction (±20°) for wide swath coverage, and in elevation to compensate for the motion of the aircraft. The calculated results, as well as the measured electrical performance over wide-angle scanning, are presented. The theoretical results (calculated) guiding the antenna optimization are based on physical optics (PO) analysis and agree well with the measurements and our design goals.