A Radio Frequency Interference Survey of Alston Observatory for Small Radio Telescopes

Abstract

Alston Observatory currently only has optical telescopes, however there is a potential for a Small Radio Telescope (SRT) for the site as a teaching aid. An investigation into the Radio Environment of the site found that around the bandwidth a telescope would observe at (1420 MHz) the noise floor is acceptable for a radio telescope being observed at -195 dBW{m2{Hz, which should be able to view objects around the same brightness as M31 in the 21cm line with a minimum 2.4m dish on the site. A few peaks of potential interference were found at 1419.649 MHz, 1420.609 MHz, and 1421.569 MHz that were consistent across the site and also in a comparison reading done in Preston, the nearby city. Although no confirmed source was found, the fact that the peaks did not change over the site and were also present in Preston indicate they may be from the survey setup, which requires further investigation. There was also interference near the main building on the site, the Planetarium, as expected, leading to a suggestion of the placement of the telescope to be on top of the Planetarium building, where RFI from the building would not be able to enter the dish, and where shielding can be placed below the telescope to minimise any interference regardless. It was also found that the current Moses Holden Telescope would not cause interference in the 1420 MHz band, meaning that both telescopes could be used concurrently if needed. A potential issue going forward however is that these results may over the next few years, with the increasing amount of satellite constellations, which could make the site unusable for radio observations at certain bands.