Selection of radio astronomical observation sites and its dependence on human generated RFI

Abstract

We investigate the influence of population density on radio-frequency interference (RFI) affecting radio astronomy. We use a new method to quantify the threshold of population density in order to determine the most suitable lower limit for site selection of a radio quiet zone (RQZ). We found that there is a certain trend in the population density-RFI graph that increases rapidly at lower values and slows down to almost flat at higher values. We use this trend to identify the thresholds for population density that produce RFI. Using this method we found that, for frequencies up to 2.8 GHz, low, medium and high population densities affecting radio astronomy are below 150 ppl km -2, between 150 ppl km-2 and 5125 ppl km-2, and above 5125 ppl km-2 respectively. We also investigate the effect of population density on the environment of RFI in three astronomical windows, namely the deuterium, hydrogen and hydroxyl lines. We find that a polynomial fitting to the population density produces a similar trend, giving similar thresholds for the effect of population density. We then compare our interference values to the standard threshold levels used by the International Telecommunication Union within these astronomical windows. © 2014 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.