Development of imaging riometers

Abstract

An 8 by 8 beam imaging riometer with a view field of 180km by 180km, spatial resolution of 20km, and time resolution of 1 to 4s has been developed in Japan. System design is described with some stress on the difference from the first imaging riometer system, IRIS, developed by the University of Maryland. This system has a unique capability of displaying absorption image on the real time basis with the aid of QL software, which is summarized in a separate paper. The performance of the array antenna system is confirmed by simulation calculations using the galactic radio noise map at 30MHz obtained by CANE (Aust. J. Phys., 31,561,1978). Procedures for absorption image forming are also described. Some of the absorption images obtained by this system are compared with optical auroral images observed at the same location at the same time. It is found that the both images show a good similarity for morning-side auroras. It is, therefore, concluded that the imaging riometer is a very useful tool for monitoring the auroral form when the optical aurora observation is difficult by the sunlit, or weather condition.