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29th of February 2024
A plot of the ASKAP observing frequencies showing the likelihood of various kinds of Radio Frequency Interference.
Survey and Monitoring of ASKAP’s RFI environment and Trends
by Lourenço et al.
Lourenço et al. present an initial analysis of Radio Frequency Interference (RFI) flagging statistics from archived Australian SKA Pathfinder (ASKAP) observations for the Survey and Monitoring of ASKAP’s RFI environment and Trends (SMART) project. The team used the telescope itself as a very sensitive RFI monitor and directly assess the fraction of scientific observations impacted by RFI. We found that the average amount of flagging due to RFI across the routinely used "clean" continuum science bands is 3%. The "clean" mid band from 1293 to 1437 MHz (excluding the 144 MHz below 1293 MHz impacted by radionavigation-satellites which is discarded before processing) is the least affected by RFI, followed by the "clean" low band from 742 to 1085 MHz. ASKAP Survey Science Projects lose most of their data to the mobile service in the low band, aeronautical service in the mid band and satellite navigation service in the 1510–1797 MHz high band. We also show that for some of these services, the percentage of discarded data has been increasing year-on-year. SMART provides a unique opportunity to study ASKAP’s changing RFI environment, including understanding and updating the default flagging behaviour, inferring the suitability of and calibrating RFI monitoring equipment, monitoring spectrum management compliance in the Australian Radio Quiet Zone – Western Australia (ARQZWA), and informing the implementation of a suite of RFI mitigation techniques.

The top panel above shows the mean probability of flagging, comparing flagging in the day (orange) versus night (blue). The middle panel shows the probability of RFI based on RFI monitors. The bottom panel shows differences in flagging between night and day (blue) and RFI monitor (opaque red dashed curve in the background). In the background of the top panel are ASKAP’s low, mid, and high bands (hatched area is discarded after observing). In the background of the second panel the broad ranges of several primary allocations affecting ASKAP. Finally, the protected band (spectral lines) in yellow and the self-generated RFI in purple are shown vertically across all panels.

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