Two-Antenna Method for Characterizing Lower Ionosphere Processes Using Incoherent Scatter Technique

We proposed a new method aiming to identify the lower ionosphere processes and estimate their parameters. For this purpose, we combined fixed and fully steerable parabolic antennas of Kharkiv incoherent scatter (IS) radar to be directed to zenith and operate simultaneously. The 100-m fixed antenna is used in both transmit and receive mode, while the fully steerable one being 25 m in diameter receives IS signal only. This enables to eliminate a negative effect of the antenna switch on measured characteristics of received signal and eventually on retrieved ionospheric parameters. Such effect is due to a gas-filled arrester tube that needs a definite time to return to a stationary state in the receive mode after the end of sounding signal transmission. The modification of radio receiver system was made by adding new radio elements to a path blanking system of the receiver connected to 25-m antenna and aims to ensure this blanking to be independent on 100-m antenna receiver path and its optimization. A number of experiments was conducted, the results of which evidence the efficiency of the proposed method for measuring characteristics of the signal scattered from the lower ionosphere. In particular, wave-like patterns in received signal power were detected at altitudes of 50-100 km. We detected factors causing a lower limit altitude for which this method can be applied. One of them is a strong interference resulted from transmitted signal reflection from a local object spaced at 41 km away. The source of such interference is found to be the Kharkiv television center tower producing the reflected signal that is received by 25-m antenna side lobe. We suggested this fully steerable antenna to be set in azimuth in such a way to achieve the minimum reflected signal level received by the side lobes.