Tobias Liaudat


Tobias Liaudat

PhD Student

Contact Information
E-mail: tobias.liaudat [at] cea [dot] fr
Office: 272
Affiliation: IRFU/DAp-AIM

Jean-Luc Starck , Martin Kilbinger



Research Interests

The main motivation of my PhD is to develop a model for Euclid's space mission Point Spread Function (PSF) that will account spatial, spectral and time variations.  This model should be able to estimate Euclid's PSF at all the galaxy positions of the satellite's Field of View (FoV) to be able to correct the effect of it on the shear galaxy measurements.

The Euclid satellite, to be launched in 2022, will be able to observe the sky in the optical and infrared, and will be able to map large scale structures and weak lensing distortions out to high redshifts. Weak gravitational lensing is a fundamental tool of cosmology to constrain models. For the mission to be successful the measurements have to be very precise and, therefore, it is vital to have a reliable PSF model.

My main interests are: Inverse problems, Image and signal processing, Point Spread Function modelling, convex and non-convex optimisation, weak lensing, etc..

Master thesis

The Master thesis was done in the CosmoStat laboratory under the supervision of Jérôme Bobin and Christophe Kervazo, where we were focused in the sparse Blind Source Separation (BSS) problem. We developed a method for tackling large scale problems (not able to scan all the observations simultaneously) which is able to parallelise the work by the use of a clever manifold-based matrix aggregation procedure. [Article]


  • Multi-CCD Point Spread Function Modelling,
    T. Liaudat, J. Bonnin, J.-L. Starck, M.A. Schmitz, A. Guinot, M. Kilbinger, S.D.J. Gwyn.
    Submitted 2020. (arXiv, code)
  • Faster and better sparse blind source separation through mini-batch optimization,
    C. Kervazo, T. Liaudat, J. Bobin.
    Digital Signal Processing, Elsevier 2020. (DSP, HAL)

Conferences & Talks

  • Distributed sparse BSS for large-scale datasets,
    T. Liaudat, J. Bobin, C. Kervazo.
    SPARS, Toulouse, France, July 1-4, 2019 (Article, Poster, code)


  • 2020-2021: Teaching assistant within the applied mathematics department DepMap from École Polytechnique.
    - Statistics MAP433


  • Masters II SISEA in Research, specialised in Image Processing, IMT Atlantique, Brest, France, September 2018.
  • Engineering degree, specialised in Image Processing, IMT Atlantique, Brest, France, September 2018.
  • Electronic engineering degree, Faculty of Engineering, University of Buenos Aires, Argentina, September 2019.

Other links


I am one of the organisers of CosmoStat's CosmosClub that is our Journal club/Group seminar. If you would like to give a talk and meet the group do not hesitate to contact me.

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