A morphological algorithm for improving radio-frequency interference detection

TL;DR

This paper introduces a morphological algorithm using the scale-invariant rank operator to enhance radio-frequency interference detection in astronomical data, improving accuracy and speed in high-resolution observatories.

Contribution

It presents a novel morphological technique with linear complexity that enhances RFI detection, integrated into the LOFAR observatory pipeline.

Findings

Improved RFI detection accuracy in radio observatory data

Algorithm has linear time complexity and high efficiency

Applicable to other source detection tasks

Abstract

A technique is described that is used to improve the detection of radio-frequency interference in astronomical radio observatories. It is applied on a two-dimensional interference mask after regular detection in the time-frequency domain with existing techniques. The scale-invariant rank (SIR) operator is defined, which is a one-dimensional mathematical morphology technique that can be used to find adjacent intervals in the time or frequency domain that are likely to be affected by RFI. The technique might also be applicable in other areas in which morphological scale-invariant behaviour is desired, such as source detection. A new algorithm is described, that is shown to perform quite well, has linear time complexity and is fast enough to be applied in modern high resolution observatories. It is used in the default pipeline of the LOFAR observatory.