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Annonce

10 décembre 2024

Stage M2 - Robust joint detection-estimation methodologies for massive radio telescopes


Catégorie : Stagiaire


M2 research internship proposal

Robust joint detection-estimation methodologies for massive radio telescopes

Internship supervisors:
  • Stefano Fortunati, SAMOVAR/TSP, stefano.fortunati@telecom-sudparis.eu.
  • Lucien Bacharach, SATIE, lucien.bacharach@universite-paris-saclay.fr.
Important dates:
  • Deadline for the submission of candidature: until mid-January,
  • Duration of the stage: from 4 to 6 months,
  • Period of the stage: from February to September 2025,

Scientific context

One of the key feature characterizing the new-generation of radio telescopes is the large number of their antenna elements. Built in 2010, the Low-Frequency Array (LOFAR) is currently the largest radio telescope in operation with 100 000 antenna dipoles distributed across several European countries [1]. Furthermore, the upcoming Square-Kilometer Array (SKA) will be made up of more than 130 000 antennas [2]. Such a large number of antennas will make it possible to acquire increasingly accurate and detailed images of the celestial vault. Such images will form the basis for promising developments in astrophysics and cosmology in the coming years.
However, as in any other “remote sensing system”, the signal collected by a radio telescope is affected by different sources of disturbance that will degrade the quality of the collected image.
Consequently, to take full advantage of the potential of the new radio telescopes, one must first take the disturbance into account. In general, this disturbance is characterized as a zeromean Gaussian random process with possibly unknown correlation structure. Unfortunately, the Gaussian assumption is often violated by some impulsive noise sources whose presence may produce a breakdown of the performance of Gaussian-based procedures. In order to take into consideration the impulsive behavior of the disturbance, different classes of heavy-tailed distributions (including the Gaussian one as a special case) has been proposed in array processing literature [3]. However, any choice of a specific heavy-tailed distribution is arbitrary to some extent, since none of them, taken individually, can fully describe the physical behavior of the disturbance.
Then, the crucial question is: would it be possible to derive robust imaging algorithms able to guarantee a predetermined level of performance without assuming any specific non-Gaussian noise model? If yes, which is the price to pay? In the context of array processing, a positive answer has been recently provided in [4]. By letting the number of antenna elements grow unboundedly, a robust test for the detection of sources of interest in heavy-tailed noise with unspecified distribution has been proposed. Roughly speaking, the findings in [4] tell us that if the number of antenna elements is sufficiently large, it is possible to derive source detection/estimation/imaging algorithms able to achieve the desired performance regardless the (generally unknown) disturbance model.

Description of the expected work

While in a classical array processing framework, having a massive amount of antenna sensors may be unrealistic due to physical constraints, the modern radio telescopes naturally fit this requirement. Consequently, this SIDEREAL project has the following two main aims:

1. Building upon the existing works such as [5–7], we will adapt the array signal model used in [4] to the context of radio telescopes. Particular attention will be devoted to the disturbance model to be used in astronomical data analysis and on its statistical description. The main goal here will be to clarify the similarities and the differences between classical array processing [4] and radio telescope [5–7] applications (e.g., detection of a target vs imaging and source reconstruction).

2. After these preliminary, but necessary, investigations, the project will focus on the development nof original detection/estimation/reconstruction algorithms for astrophysical sources exploiting the massive number of antenna elements available in modern radio telescopes.

Their performance and statistical properties will be assessed by means of simulated data.

Required profile:

Master 2 or equivalent in statistical signal processing or any related field.

References

[1] van Haarlem, M. P. and al., “Lofar: The low-frequency array,” A&A, vol. 556, p. A2, 2013.
[2] P. E. Dewdney, P. J. Hall, R. T. Schilizzi, and T. J. L. W. Lazio, “The square kilometre array,” Proceedings of the IEEE, vol. 97, no. 8, pp. 1482–1496, 2009.
[3] E. Ollila, D. E. Tyler, V. Koivunen, and H. V. Poor, “Complex elliptically symmetric distributions: Survey, new results and applications,” IEEE Transactions on Signal Processing, vol. 60, no. 11, pp. 5597–5625, 2012.
[4] S. Fortunati, L. Sanguinetti, F. Gini, M. S. Greco, and B. Himed,“Massive MIMO radar for target detection,” IEEE Transactions on Signal Processing, vol. 68, pp. 859–871, 2020.
[5] S. J. Wijnholds and A.-J. van der Veen, “Multisource self-calibration for sensor arrays,” IEEE Transactions on Signal Processing, vol. 57, no. 9, pp. 3512–3522, 2009.
[6] S. J. Wijnholds and A.-J. van der Veen, “Fundamental imaging limits of radio telescope arrays,” IEEE Journal of Selected Topics in Signal Processing, vol. 2, no. 5, pp. 613–623, 2008.
[7] A. Leshem and A.-J. van der Veen, “Radio-astronomical imaging in the presence of strong radio interference,” IEEE Transactions on Information Theory, vol. 46, no. 5, pp. 1730–1747, 2000.

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