URAN, A Decameter Band VLBI System

Extract

Until recently, regular interferometric measurements were not performed at decameter wavelengths. The reasons are well known, i.e., effects of the ionosphere and the interplanetary plasma, the inherently high level of interference and of the galactic background, and the necessity to have very large antennas. Yet, because of the considerable interest in such observations, the Ukrainian SSR Academy of Sciences has started a project aimed at the development and construction of a system of decameter band interferometers (project URAN, from the “Ukrainian Radio Interferometers of Academy of Sciences (Nauk)”). By 1989, the system will involve four interferometers with baseline lengths between 40 and 900 km. The basic instrument of all these is the N–S arm of the large UTR-2 radio telescope operated by the Institute of Radio Astronomy in Kharkov. The antenna is an electrically controlled phased array of broad band dipoles (total length about 1800 m). At the other sites, the antennas are smaller phased arrays (maximum length about 230 m) consisting of crossed dipoles.