Gain calibration methods for radio telescope arrays

Boonstra, Albert‐Jan; Veen, Alle-Jan van der

doi:10.1109/tsp.2002.806588

Cited by 76 publications

(88 citation statements)

References 11 publications

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“…One of these compromises will be the number of sources peeled every 8 seconds. Several methods for calibrating antenna gains are compared in [26]. These are alternatives to the technique discussed in section III-C.…”

Section: Discussion Performancementioning

confidence: 99%

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Real-Time Calibration of the Murchison Widefield Array

Mitchell

Greenhill

Wayth

et al. 2008

IEEE J. Sel. Top. Signal Process.

209

266

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Abstract-The interferometric technique known as peeling addresses many of the challenges faced when observing with low-frequency radio arrays, and is a promising tool for the associated calibration systems. We investigate a real-time peeling implementation for next-generation radio interferometers such as the Murchison Widefield Array (MWA). The MWA is being built in Australia and will observe the radio sky between 80 and 300 MHz. The data rate produced by the correlator is just over 19 GB/s (a few Peta-Bytes/day). It is impractical to store data generated at this rate, and software is currently being developed to calibrate and form images in real time. The software will run on-site on a high-throughput real-time computing cluster at several tera-flops, and a complete cycle of calibration and imaging will be completed every 8 seconds. Various properties of the implementation are investigated using simulated data. The algorithm is seen to work in the presence of strong galactic emission and with various ionospheric conditions. It is also shown to scale well as the number of antennas increases, which is essential for many upcoming instruments. Lessons from MWA pipeline development and processing of simulated data may be applied to future low-frequency fixed dipole arrays.

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Section: Discussion Performancementioning

confidence: 99%

“…The technique that required the fewest computations was the logarithmic least squares (LOGLS) algorithm, which scaled as N 2 a . The numbers given in [26] for a single polarization version are 2N 2 a multiplications with an additional 16N 2 a for weighting. How does this compare to the algorithm discussed in section III-C?…”

Section: Discussion Performancementioning

confidence: 99%

Real-Time Calibration of the Murchison Widefield Array

Mitchell

Greenhill

Wayth

et al. 2008

IEEE J. Sel. Top. Signal Process.

209

266

View full text Add to dashboard Cite

show abstract

“…Given R, we can solve for g and Σ n in several ways [24]- [26]. E.g., any submatrix away from the diagonal is only dependent on g and is rank 1: this allows direct estimation of g. In the more general case described by (3), multiple calibrators may be simultaneously present.…”

Section: Scenariomentioning

confidence: 99%

Calibration challenges for future radio telescopes

Wijnholds

Tol

Nijboer

et al. 2010

IEEE Signal Process. Mag.

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“…The state-of-the-art consists in the so-called alternating least squares approach [24]- [27], which leads to statistically efficient algorithm under a Gaussian model, since the least squares estimator is equivalent to the maximum likelihood (ML) estimator in this case. On the other hand, expectation maximization (EM) [28]- [30] and EM-based algorithms, such as the space alternating generalized expectation maximization algorithm [31], have been proposed in order to enhance the convergence rate of the least squares-based calibration algorithms [32].…”

Section: Introductionmentioning

confidence: 99%

Robust Calibration of Radio Interferometers in Non-Gaussian Environment

Ollier

Korso²,

Boyer

et al. 2017

IEEE Trans. Signal Process.

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Abstract-The development of new phased array systems in radio astronomy, as the low frequency array (LOFAR) and the square kilometre array (SKA), formed of a large number of small and flexible elementary antennas, has led to significant challenges. Among them, model calibration is a crucial step in order to provide accurate and thus meaningful images and requires the estimation of all the perturbation effects introduced along the signal propagation path, for a specific source direction and antenna position. Usually, it is common to perform model calibration using the a priori knowledge regarding a small number of known strong calibrator sources but under the assumption of Gaussianity of the noise. Nevertheless, observations in the context of radio astronomy are known to be affected by the presence of outliers which are due to several causes, e.g., weak noncalibrator sources or man made radio frequency interferences. Consequently, the classical Gaussian noise assumption is violated leading to severe degradation in performances. In order to take into account the outlier effects, we assume that the noise follows a spherically invariant random distribution. Based on this modeling, a robust calibration algorithm is presented in this paper. More precisely, this new scheme is based on the design of an iterative relaxed concentrated maximum likelihood estimation procedure which allows to obtain closed-form expressions for the unknown parameters with a reasonable computational cost. This is of importance as the number of estimated parameters depends on the number of antenna elements, which is large for the new generation of radio interferometers. Numerical simulations reveal that the proposed algorithm outperforms the state-of-theart calibration techniques.

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Gain calibration methods for radio telescope arrays

Cited by 76 publications

References 11 publications

Real-Time Calibration of the Murchison Widefield Array

Real-Time Calibration of the Murchison Widefield Array

Calibration challenges for future radio telescopes

Robust Calibration of Radio Interferometers in Non-Gaussian Environment

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