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An interference detection strategy for Apertif based on AOFlagger 3 | A. R. Offringa
; B. Adebahr
; A. Kutkin
; E. A. K. Adams
; T. A. Oosterloo
; J. M. van der Hulst
; H. Dénes
; C. G. Bassa
; D. L. Lucero
; W. J. G. Blok
; K. M. Hess
; J. van Leeuwen
; G. M. Loose
; Y. Maan
; L. C. Oostrum
; E. Orrú
; D. Vohl
; J. Ziemke
; | Date: |
4 Jan 2023 | Abstract: | Context. Apertif is a multi-beam receiver system for the Westerbork Synthesis
Radio Telescope that operates at 1.1-1.5 GHz, which overlaps with various radio
services, resulting in contamination of astronomical signals with
radio-frequency interference (RFI). Aims. We analyze approaches to mitigate
Apertif interference and design an automated detection procedure for its
imaging mode. Using this approach, we present long-term RFI detection results
of over 300 Apertif observations. Methods. Our approach is based on the
AOFlagger detection approach. We introduce several new features, including ways
to deal with ranges of invalid data (e.g. caused by shadowing) in both the
SumThreshold and scale-invariant rank operator steps; pre-calibration bandpass
calibration; auto-correlation flagging; and HI flagging avoidance. These
methods are implemented in a new framework that uses the Lua language for
scripting, which is new in AOFlagger version 3. Results. Our approach removes
RFI fully automatically, and is robust and effective enough for further
calibration and (continuum) imaging of these data. Analysis of 304 observations
show an average of 11.1% of lost data due to RFI with a large spread. We
observe 14.6% RFI in auto-correlations. Computationally, AOFlagger achieves a
throughput of 370 MB/s on a single computing node. Compared to published
machine learning results, the method is one to two orders of magnitude faster. | Source: | arXiv, 2301.01562 | Services: | Forum | Review | PDF | Favorites |
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