Marcellin Atemkeng

Marcellin Atemkeng

Office Room 19 Maths Building (Drostdy Lodge)

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Posts

Future Blog Post

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Blog Post number 4

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Blog Post number 2

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Blog Post number 1

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publications

Fast algorithms to approximate the position-dependent point spread function responses in radio interferometric wide-field imaging

Published in Monthly Notices of the Royal Astronomical Society, 2020

The desire for wide-field of view, large fractional bandwidth, high sensitivity, high spectral and temporal resolution has driven radio interferometry to the point of big data revolution where the data is represented in at least three dimensions with an axis for spectral windows, baselines, sources, etc; where each axis has its own set of sub-dimensions. The cost associated with storing and handling these data is very large, and therefore several techniques to compress interferometric data and/or speed up processing have been investigated. Unfortunately, averaging-based methods for visibility data compression are detrimental to the data fidelity, since the point spread function (PSF) is position-dependent, i.e. distorted and attenuated as a function of distance from the phase centre. The position dependence of the PSF becomes more severe, requiring more PSF computations for wide-field imaging. Deconvolution algorithms must take the distortion into account in the major and minor cycles to properly subtract the PSF and recover the fidelity of the image. This approach is expensive in computation since at each deconvolution iteration a distorted PSF must be computed. We present two algorithms that approximate these position-dependent PSFs with fewer computations. The first algorithm approximates the position-dependent PSFs in the uv-plane and the second algorithm approximates the position-dependent PSFs in the image-plane. The proposed algorithms are validated using simulated data from the MeerKAT telescope.

Recommended citation: Atemkeng, M., Smirnov, O., Tasse, C., Foster, G., & Makhathini, S. (2020). "Monthly Notices of the Royal Astronomical Society</i>. https://arxiv.org/abs/2009.07010

Xova: Baseline-Dependent Time and Channel Averaging for Radio Interferometry

Published in Proceedings of the Astronomical Data Analysis Software and Systems (ADASS) conference, 2021

Xova is a software package that implements baseline-dependent time and channel averaging on Measurement Set data. The uv-samples along a baseline track are aggregated into a bin until a specified decorrelation tolerance is exceeded. The degree of decorrelation in the bin correspondingly determines the amount of channel and timeslot averaging that is suitable for samples in the bin. This necessarily implies that the number of channels and timeslots varies per bin and the output data loses the rectilinear input shape of the input data.

Recommended citation: Atemkeng, M., Perkins, S., Kenyon, J., Hugo, B. and Oleg Smirnov (2021). "Xova: Baseline-Dependent Time and Channel Averaging for Radio Interferometry." Proceedings of the Astronomical Data Analysis Software and Systems (ADASS) conference. https://arxiv.org/abs/2101.11270

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