This is a visualization and RFI mitigation tool of the Netherlands eScience center eAstronomy project.

This tool can convert and visualize radio astronomy measurement sets (i.e. visibilities), as well as most LOFAR intermediate data products, such as raw voltages, filtered data and beam formed data. In addition, this tool can perform RFI mitigation.

In addition, this repository contains the real-time RFI mitigation code developed for LOFAR, in the directory LOFAR-source.

Finally, we have developed a GPU prototype version of the code as well. This code was developed by Linus Schoemaker in the context of his masters project. The code is in the directory GPU-source.

All code is distributed under the Apache 2.0 licence.

Please cite as:

Rob V. van Nieuwpoort and the LOFAR team: Exascale Real-Time Radio Frequency Interference Mitigation Exascale Radio Astronomy, AAS Topical Conference Series Vol. 2. Proceedings of the conference held 30 March - 4 April, 2014 in Monterey, California. Bulletin of the American Astronomical Society, Vol. 46, #3, #403.01

The slides used at the conference are available in the doc directory in this package, and are available online here:

http://vannieuwpoort.com/papers/Exascale-Astronomy-2014-Monterey-RFI.pdf

The abstract of this article is here:

http://adsabs.harvard.edu/abs/2014era..conf40301V

The abstract is shown below as well.

Exascale Real-Time Radio Frequency Interference Mitigation

Radio Frequency Interference (RFI) mitigation is extremely important to take advantage of the vastly improved bandwidth, sensitivity, and field-of-view of exascale telescopes. For current instruments, RFI mitigation is typically done offline, and in some cases (partially) manually. At the same time, it is clear that due to the high bandwidth requirements, RFI mitigation will have to be done automatically, and in real-time, for exascale instruments.

In general, real-time RFI mitigation will be less precise than offline approaches. Due to memory constraints, there is much less data to work with, typically only in the order of one second or less, as opposed to the entire observation. In addition, we can record only limited statistics of the past. Moreover, we will typically have only few frequency channels locally available at each compute core. Finally, the amount of processing that can be spent on RFI mitigation is extremely limited due to computing and power constraints. Nevertheless, there are potential benefits as well, which include the possibility of working on higher time and frequency resolutions before any integration is done, leading to more accurate results. Most importantly, we can remove RFI before beam forming, which combines data from all receivers. The RFI that is present in the data streams from the separate receivers is also combined, effectively taking the union of all RFI. Thus, the RFI from all receivers pollutes all beams. Therefore, it is essential to do real-time RFI mitigation before the beam former. This is particularly important for pulsar surveys, for instance. modes.

Although our techniques are generic, we describe how we implemented real-time RFI mitigation for one of the SKA pathfinders: The Low Frequency Array (LOFAR). The RFI mitigation algorithms and operations we introduce here are extremely fast, and the computational requirements scale linearly in the number of samples and frequency channels. We evaluate the quality of the algorithms with real LOFAR pulsar observations. By comparing the signal-to-noise ratios of the folded pulse profiles, we can quantitatively compare the impact of real-time RFI mitigation, and compare different algorithms.

Copyright 2016 The Netherlands eScience Center

Written by Rob van Nieuwpoort, r.v.van.nieuwpoort@liacs.leidenuniv.nl