The rapid development of communication technology escalates the challenges for the radio astronomy observing environment. During pulsar observations, transient radio frequency interference (RFI) sometimes appears in the observational data obtained from the NanShan 26-m Radio Telescope (NSRT) at the Nanshan Station of Xinjiang Astronomical Observatory (XAO).
Recently, SONG Yining, a postgraduate student under the supervision of Dr. WANG Na and Dr. LIU Zhiyong, along with Dr. Rai Yuen and PhD student LI Jun from XAO, proposed an algorithm, referred to as the pulsar phase and standard deviation (PPSD), which can efficiently mitigate transient RFI in pulsar data.
The basic idea of the algorithm is to use a high-precision pulsar ephemeris model to accurately obtain the phase and profile information of the pulsar in the observation data, which are then combined with the pulsar dispersion delay to determine the on-pulse range in different frequency sub-bands.
Accordingly, the original signal data within the on-pulse range
is not affected by the RFI mitigation algorithm. Then, through iteration, the mean value and standard deviation
of the off-pulses are calculated and used to set the thresholds, based on 3
rule, for determining the data points that are outside the threshold as RFI and mitigating them. Mitigation of the transient RFI is considered complete when all noise data are within the latest threshold. Finally, random data points that obey Gaussian white noise are generated to substitute for the RFI. The Workflow is shown in Figure. 1.
The algorithm is effective in identifying and mitigating transient RFI within off-pulses, thus effectively improves the signal-to-noise ratio of pulsar observation (Figure.2) and significantly improves the efficiency of transient RFI mitigation.
Figure 1. Workflow of the PPSD algorithm.
Figure 2. Comparison of the profile of PSR J0332+5434 before (upper row) and after (lower row) mitigation of the transient RFI using PPSD. Left column: phase vs. frequency; middle column: the average profile before de-dispersion; right column: the average profile after de-dispersion.
Contact: SONG Yining
Xinjiang Astronomical Observatory, Chinese Academy of Sciences
E-mail: songyining@xao.ac.cn
Web: https://doi.org/10.3847/1538-4357/ac3329
