A new approach to mitigation of radio frequency interference in interferometric data

Abstract

Radio frequency interference (RFI) is the principal factor limiting the sensitivities of radio telescopes, particularly at frequencies below 1 GHz. I present a conceptually new approach to mitigation of RFI in interferometric data. This has been used to develop a software tool (RfiX) to remove RFI from observations using the Giant Metrewave Radio Telescope, India. However, the concept can be used to excise RFI in any interferometer. Briefly, the fringe-stopped correlator output of an interferometer baseline oscillates with the fringe-stop period in the presence of RFI. RfiX works by identifying such a pattern and subtracting it from the data. It is perhaps the only purely software technique which can salvage the true visibility value from RFI-corrupted data. It neither requires high-speed hardware nor real-time processing and works best on normal correlator output integrated for 1-10s. It complements other mitigation schemes with its different approach and the regime it addresses. Its ability to work with data integrated over many seconds gives it an advantage while excising weak, persistent RFI unlike most other techniques which use high-speed sampling to localise RFI in time-frequency plane. RfiX is also different in that it does not require RFI-free data to identify corrupted sections. Some results from the application of RfiX is presented including an image at 240 MHz with a Peak/noise ratio of 43000, the highest till date at wavelengths >1m.

Accepted for Publication in the Astrophysical Journal

References in corpus (6)

• Multichannel interference mitigation methods in radio astronomy
• Removing radio interference from contaminated astronomical spectra using an independent reference signal and closure relations
• Radio Frequency Interference Mitigation at the WSRT
• Statistically Stable Estimates of Variance in Radioastronomical Observations as Tools for RFI Mitigation
• RFI detection by automated feature extraction and statistical analysis
• RFI Identification and Mitigation Using Simultaneous Dual Station Observations

Cited by in corpus (21)

• Post-correlation radio frequency interference classification methods
• The "toothbrush-relic": evidence for a coherent linear 2-Mpc scale shock wave in a massive merging galaxy cluster?
• VAST: An ASKAP Survey for Variables and Slow Transients
• Radio continuum observations of new radio halos and relics from the NVSS and WENSS surveys
• A double radio relic in the merging galaxy cluster ZwCl 0008.8+5215
• Discovery of spectral curvature in the shock downstream region: CIZA J2242.8+5301
• Deep Low-Frequency Radio Observations of the NOAO Bootes Field: I. Data Reduction and Catalog Construction
• Absolving the SSINS of Precision Interferometric Radio Data: A New Technique for Mitigating Faint Radio Frequency Interference
• 153 MHz GMRT follow-up of steep-spectrum diffuse emission in galaxy clusters
• Post-correlation filtering techniques for off-axis source and RFI removal
• Radio Observations of HD 80606 Near Planetary Periastron
• SERPent: Automated reduction and RFI-mitigation software for e-MERLIN
• A distant radio mini-halo in the Phoenix galaxy cluster
• Implementing RFI mitigation in Radio Science
• Detection of off-pulse emission from PSR B0525+21 and PSR B2045-16
• The discovery of a radio halo in PLCK G147.3-16.6 at z=0.65
• Trajectory Based RFI Subtraction and Calibration for Radio Interferometry
• Very Large Array Observations of Disturbed Ion Flow from the Plasmasphere to the Nighttime Ionosphere
• Timing calibration and spectral cleaning of LOFAR time series data
• Two procedures to flag radio frequency interference in the UV plane
• TABASCAL: Removing multi-satellite interference from radio interferometry observations