Improved Modeling for Moving Sources of Radio Frequency Interference and Impact on Flagging Strategies

Abstract

Radio frequency interference (RFI) is a major challenge for low-frequency radio experiments targeting the redshifted 21-cm signal from the Epoch of Reionization. Many important RFI sources, including aircraft and satellites, move across the sky during an observation. The averaging of visibilities for such moving sources over a finite correlator integration produces a distinct sinc-like pattern in the interferometric uv-plane, causing the RFI to appear bright on some baselines and strongly suppressed on others. Here, we develop an analytical model for this effect and validate its qualitative behavior against real MWA observations and numerical simulations. Controlled RFI injections into clean MWA data are then used to compare several flagging treatments in the context of EoR power spectrum recovery. These treatments explore the trade-off between per-baseline flagging, which can miss weak but potentially non-negligible contamination on baselines where the integration effect leads to strong suppression, and baseline-aggregated flagging, which removes more faint residual contamination but reduces the total number of usable uv-modes. We find that the preferred strategy depends on RFI brightness and occupancy, but that flagging all frequencies at contaminated time-steps most consistently minimizes excess power for bright or frequent events. However, none of the tested flagging treatments fully recovers the uncontaminated reference spectrum, motivating future work on direct modeling and subtraction of moving RFI sources.