Real-time RFI Mitigation in Radio Astronomy

As the use of wireless technology has increased around the world, Radio Frequency Interference (RFI) has become more and more of a problem for radio astronomers. Preventative measures exist to limit the presence of RFI, and programs exist to remove it from saved data, but the use of algorithms to detect and remove RFI as an observation is occurring is much less common. Such a method would be incredibly useful for observations in which the data must undergo several rounds of processing before being saved, as in pulsar timing studies. Strategies for real-time mitigation have been discussed and tested with simulated data, but ideally the results of any approach would be validated by a detailed comparison of the final data products with and without mitigation applied. The goal of this project is to develop an RFI mitigation approach based on strategies suggested by Buch et al.(2016) and to test this program on real data from the observation of pulsar J1713+0747 at the Green Bank Observatory in West Virginia. We use a Median Absolute Deviation (MAD) filter to identify interference in the observation and replace the compromised data with random Gaussian noise to match a characteristic radio signal from space. In order to verify our results, we analyze the pulsar’s timing residuals obtained both from the mitigated data and from data processed through offline RFI removal software. Comparing the two, our preliminary findings indicate that our program is able to significantly improve the quality of timing results from the observation

A Prototype for Real-Time RFI Mitigation for Single-Dish Radio Telescopes

International audienceRadio Frequency Interference (RFI) is a profound obstacle for radio astronomy, corrupting otherwise useful observations. The increase in wireless technologies only serves to exacerbate this issue. Single-dish radio telescopes are especially vulnerable to RFI in comparison to interferometers, which inherently due to the spatial separation of their antennas have less susceptibility to interference. In this paper, we present and prototype a real-time RFI mitigation strategy for complex raw voltage time samples streaming from single-dish radio telescopes. Impulsive RFI is mitigated in the time domain. For narrowband RFI, we perform a Fourier transform, and mitigate in the frequency domain. We use a combination of techniques, include a “robust recursive power” estimator, coupled with strong and weak Bernoulli detectors; median absolute deviation determination and outlier detection; and spectral kurtosis. Corrupted voltage samples are replaced with random Gaussian noise. The prototype successfully mitigates broadband RFI in the time domain and narrowband RFI in the frequency domain.The astronomical consequences of real-time RFI mitigation are investigated. To conduct the study, 1.28TB of L band 0.16µs complex voltage samples were obtained from the GUPPI backend of the Green Bank Telescope. These observations are of the millisecond pulsar, Pulsar J1713+0747. Preliminary analysis indicates that the RFI-mitigated data produces improved pulsar residuals, compared to both unprocessed data and the current RFI mitigation post-processing software.The promising results encourage development from prototype to real-time implementation. The Python prototype runs 95x slower than real-time, as it does not utilize any parallel programming. A CUDA implementation wrapped in the Hybrid Task Graph Scheduler software is rapidly being created to exploit parallel structures in the data. Expected speed increases will reduce runtime to real-time

Real-Time RFI Mitigation in Pulsar Observations

International audienceAs the use of wireless technology has increased around the world, RadioFrequency Interference (RFI) has become more and more of a problem forradio astronomers. Preventative measures exist to limit the presence ofRFI, and programs exist to remove it from saved data, but the routineuse of algorithms to detect and remove RFI as an observation isoccurring is much less common. Such a method would be incredibly usefulfor observations in which the data must undergo several rounds ofprocessing before being saved, as in pulsar timing studies. Strategiesfor real-time mitigation have been discussed and tested with simulateddata (Buch et al., 2016), but ideally the results of any approach wouldbe validated by a detailed comparison of the final data products - forpulsar timing, the variance in the pulse times of arrival (TOAs) - withand without mitigation applied. The goal of this project is to developan RFI mitigation approach based on the previously suggested strategiesand test this program on actual data from the observation of pulsarJ1713+0747. We use a Median Absolute Deviation (MAD) filter to identifyinterference in the observation and replace the compromised data withrandom Gaussian noise to match a characteristic radio signal from space.In order to verify our results, we analyze the pulsar?s TOAs obtainedboth from the mitigated data and from the unmitigated data processedthrough offline RFI removal software. Comparing the two, our preliminaryfindings indicate that our program is able to improve the quality oftiming results from the observation. <P /&gt

A Prototype for Real-Time RFI Mitigation for Single-Dish Radio Telescopes

International audienceRadio Frequency Interference (RFI) is a profound obstacle for radio astronomy, corrupting otherwise useful observations. The increase in wireless technologies only serves to exacerbate this issue. Single-dish radio telescopes are especially vulnerable to RFI in comparison to interferometers, which inherently due to the spatial separation of their antennas have less susceptibility to interference. In this paper, we present and prototype a real-time RFI mitigation strategy for complex raw voltage time samples streaming from single-dish radio telescopes. Impulsive RFI is mitigated in the time domain. For narrowband RFI, we perform a Fourier transform, and mitigate in the frequency domain. We use a combination of techniques, include a “robust recursive power” estimator, coupled with strong and weak Bernoulli detectors; median absolute deviation determination and outlier detection; and spectral kurtosis. Corrupted voltage samples are replaced with random Gaussian noise. The prototype successfully mitigates broadband RFI in the time domain and narrowband RFI in the frequency domain.The astronomical consequences of real-time RFI mitigation are investigated. To conduct the study, 1.28TB of L band 0.16µs complex voltage samples were obtained from the GUPPI backend of the Green Bank Telescope. These observations are of the millisecond pulsar, Pulsar J1713+0747. Preliminary analysis indicates that the RFI-mitigated data produces improved pulsar residuals, compared to both unprocessed data and the current RFI mitigation post-processing software.The promising results encourage development from prototype to real-time implementation. The Python prototype runs 95x slower than real-time, as it does not utilize any parallel programming. A CUDA implementation wrapped in the Hybrid Task Graph Scheduler software is rapidly being created to exploit parallel structures in the data. Expected speed increases will reduce runtime to real-time

Real-Time RFI Mitigation in Pulsar Observations

International audienceAs the use of wireless technology has increased around the world, RadioFrequency Interference (RFI) has become more and more of a problem forradio astronomers. Preventative measures exist to limit the presence ofRFI, and programs exist to remove it from saved data, but the routineuse of algorithms to detect and remove RFI as an observation isoccurring is much less common. Such a method would be incredibly usefulfor observations in which the data must undergo several rounds ofprocessing before being saved, as in pulsar timing studies. Strategiesfor real-time mitigation have been discussed and tested with simulateddata (Buch et al., 2016), but ideally the results of any approach wouldbe validated by a detailed comparison of the final data products - forpulsar timing, the variance in the pulse times of arrival (TOAs) - withand without mitigation applied. The goal of this project is to developan RFI mitigation approach based on the previously suggested strategiesand test this program on actual data from the observation of pulsarJ1713+0747. We use a Median Absolute Deviation (MAD) filter to identifyinterference in the observation and replace the compromised data withrandom Gaussian noise to match a characteristic radio signal from space.In order to verify our results, we analyze the pulsar?s TOAs obtainedboth from the mitigated data and from the unmitigated data processedthrough offline RFI removal software. Comparing the two, our preliminaryfindings indicate that our program is able to improve the quality oftiming results from the observation. <P /&gt

Real-Time RFI Mitigation for Single-Dish Radio Telescopes

International audienc

Real-Time RFI Mitigation for Single-Dish Radio Telescopes

International audienc