An RFI Mitigation Pipeline for CRAFTS Multi-beam Data Based on Signal Cross-Correlation Function and SumThreshold Algorithm

Abstract

The increasing radio frequency interference (RFI) is a well-recognized problem in radio astronomy research (Barnbaum & Bradley 1998; Briggs et al. 2000). Pulsars and Fast Radio Bursts (FRBs) are high-priority science targets of the ongoing Commercial Radio Astronomy FAST Survey (CRAFTS) (Li et al. 2018). To improve the quality of RFI removal in searches of pulsars and FRBs based on CRAFTS multibeam data, we here propose an intuitive but powerful RFI mitigation pipeline (CCF-ST). The ”CCF-ST” is a spatial filter constructed by signal cross-correlation function (CCF) and Sum-Threshold (ST) algorithm (Offringa et al. 2010). The RFI marking result is saved in a ’mask’ file, a binary format for RFI masks in PRESTO (Ransom 2001; Ransom et al. 2002, 2003). Three known pulsars,
PSR B0525-21, PSR B0621-04, and PSR J0943+2252 from CRAFTS L-band 19 beams data are used for evaluation of the performance of CCF-ST in comparison with other methods, such as PRESTO’s ’rfifind’, ArPLS-ST (Zeng et al. 2020) and ArPLS-SF (Wang et al. 2022).
The result shows that CCF-ST can reduce effective data loss rate and improves the detected signal-to-noise ratio (SNR) of the pulsations by ∼26% and ∼18% respectively compared with PRESTO’s ’rfifind’ and ArPLS-ST. The CCF-ST also has the advantage of low computational cost, e.g. reducing the time consumption by ∼40% and memory consumption by ∼90% compared with ArPLS-SF. We expect that the new RFI mitigation and analysis toolkit (CCF-ST) demonstrated in this paper can be applied to CRAFTS and other multi-beam telescope observations to improve the data quality and efficiency of pulsar and FRB searches.