Dr. Joel Sanchez-Bermudez Profile

Dr. Joel Sanchez-Bermudez

at Instituto de Astronomía (IA-UNAM)

SPIE Involvement:

Conference Chair | Editor | Author

Proceedings Article | 29 August 2022 Poster

Grism design for improving the spectral capabilities of GRAVITY+ at the VLTI

Joel Sanchez-Bermudez, Rebeca García-López, Salvador Cuevas, Frank Eisenhauer, Christian Straubmeier, Senol Yazici

Proceedings Volume 12183, 1218324 (2022) https://doi.org/10.1117/12.2630204

KEYWORDS: Interferometers, Spectral resolution, Prisms, Optical filters, Observatories, Laser optics, Large telescopes, Interferometry, Germanium, Astronomy

Proceedings Article | 26 August 2022 Presentation + Paper

CASSINI-AUTOMAP: a novel image reconstruction algorithm for infrared interferometry

Joel Sanchez-Bermudez, Antxon Alberdi, Rainer Schödel, Anand Sivaramakrishnan

Proceedings Volume 12183, 121831K (2022) https://doi.org/10.1117/12.2629488

KEYWORDS: Interferometry, Image restoration, Infrared imaging, Neural networks, Reconstruction algorithms, Neurons, Visibility, Network architectures

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Interferometry delivers the highest angular resolution. It is being used extensively in radio astronomy and, since about a decade, it is becoming an important player in infrared astronomy. However, infrared interferometry is restricted to sparse arrays and no full-phase information is recovered. While imaging is arguably the most intuitive way to analyze interferometric data, recovering images from sparsely sampled visibilities is an “ill-posed" problem. The current algorithms work under the framework of using regularized minimization techniques. These algorithms strongly depend on the priors and hyperparameters pre-defined. This gives rise to ambiguities and artifacts in the interpretation of the images and limits their accuracy/precision as well as their signal-to-noise ratio if the priors/regularizers are not well-defined. Also, it means that imaging is the domain of a handful of highly experienced astronomers, thus keeping the interferometric community small. CASSINI-AUTOMAP aims at disrupting this situation by creating a novel framework for interferometric image reconstruction. This project is based on the exploitation of the compressibility of a signal (following the principles of theory of Compressed Sensing) with a novel optimization scheme supported by Neural Networks. In particular, we focus our efforts in designing a Neural Network with adaptive activation functions to find an optimal mapping system between the infrared interferometric data and the reconstructed images. The online adaptability of the Neural Network frees us from having to rely on strong priors, making the reconstructions more accurate and less dependent on users' inputs. Our preliminary network architecture has been tested with Sparse Aperture Masking (SAM) data taken with the infrared camera NACO at the Very Large Telescope and it demonstrates the potential and reliability of the algorithm by recovering the interferometric observables. Future improvements on the software aims at analyzing data from instruments like GRAVITY at the Very Large Telescope Interferometer or the Sparse Aperture Masking mode of the James Webb Space Telescope.

Proceedings Article | 26 August 2022 Presentation + Paper

Optical interferometry imaging contest IX

J. Sanchez-Bermudez, A. Mérand, S. Sallum, J. Drevon, J. Kluska, F. Millour, P. Vermot, J. Young

Proceedings Volume 12183, 121831G (2022) https://doi.org/10.1117/12.2629430

KEYWORDS: Image restoration, Interferometry, James Webb Space Telescope, Visibility, Data modeling, Optical interferometry, Telescopes, Stars, Device simulation, Astronomy

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Proceedings Article | 13 December 2020 Presentation + Paper

Compressed sensing for infrared interferometric imaging

Joel Sanchez-Bermudez, Abel Rosales-Guzmán, Héctor Morales, Antxon Alberdi, Anand Sivaramakrishnan, Rainer Schödel, Jörg-Uwe Pott

Proceedings Volume 11446, 114461O (2020) https://doi.org/10.1117/12.2560089

KEYWORDS: Interferometry, Compressed sensing, Infrared imaging, Infrared radiation, Infrared sensors, James Webb Space Telescope, Infrared telescopes, Telescopes, Large telescopes, Interferometers

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Proceedings Article | 4 August 2016 Paper

The 2016 interferometric imaging beauty contest

J. Sanchez-Bermudez, E. Thiébaut, K.-H. Hofmann, M. Heininger, D. Schertl, G. Weigelt, F. Millour, A. Schutz, A. Ferrari, M. Vannier, D. Mary, J. Young

Proceedings Volume 9907, 99071D (2016) https://doi.org/10.1117/12.2231982

KEYWORDS: Image restoration, Interferometry, Optical interferometry, Image restoration, Reconstruction algorithms, Device simulation, Stars, Visibility, Image quality, Image processing, Spatial frequencies

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Proceedings Article | 4 August 2016 Paper

Imaging capabilities of the VLTI/MATISSE spectro-interferometric instrument

J. Sanchez-Bermudez, J.-U. Pott, R. van Boekel, T. Henning, F. Baron, A. Matter, B. Lopez, F. Millour, G. Weigelt, K.-H. Hofmann, D. Schertl

Proceedings Volume 9907, 99070B (2016) https://doi.org/10.1117/12.2232308

KEYWORDS: Image restoration, Interferometry, Interferometers, Mid-IR, Visibility, Image processing, Spatial frequencies, Data modeling, Image quality, Signal to noise ratio

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Proceedings Article | 3 August 2016 Paper

VISIR upgrade overview: all's well that ends well

Florian Kerber, Hans Ulrich Käufl, Konrad Tristram, Daniel Asmus, Pedro Baksai, Nicola Di Lieto, Danuta Dobrzycka, Philippe Duhoux, Gert Finger, Christian Hummel, Derek Ives, Gerd Jakob, Lars Lundin, Dimitri Mawet, Leander Mehrgan, Eric Pantin, Miguel Riquelme, Joel Sanchez, Stefan Sandrock, Ralf Siebenmorgen, Jörg Stegmeier, Alain Smette, Julian Taylor, Mario van den Ancker, Guillermo Valdes, Lars Venema

Proceedings Volume 9908, 99080D (2016) https://doi.org/10.1117/12.2232441

KEYWORDS: Sensors, Mid-IR, Imaging spectroscopy, Detector arrays, Imaging systems, Image quality, Telescopes, Coronagraphy, Stars, Spectroscopy

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We present an overview of the VISIR instrument after its upgrade and return to science operations. VISIR is the midinfrared imager and spectrograph at ESO’s VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan was based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array manufactured by Raytheon. In addition, a new prism spectroscopic mode covers the whole N-band in a single observation. Finally, new scientific capabilities for high resolution and high-contrast imaging are offered by sub-aperture mask and coronagraphic modes. In order to make optimal use of favourable atmospheric conditions, a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012, it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise. It is inherent to the design chosen for this detector and cannot be remedied by changing the detector set-up. Since this is a form of correlated noise, its impact can be limited by modulating the scene recorded by the detector. After careful analysis, we have implemented fast (up to 4 Hz) chopping with field stabilization using the secondary mirror of the VLT. During commissioning, the upgraded VISIR has been confirmed to be more sensitive than the old instrument, and in particular for low-resolution spectroscopy in the N-band, a gain of a factor 6 is realized in observing efficiency. After overcoming several additional technical problems, VISIR is back in Science Operations since April 2015. In addition an upgrade of the IT infrastructure related to VISIR has been conducted in order to support burst-mode operations. Science Verification of the new modes was performed in Feb 2016. The upgraded VISIR is a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It offers synergies with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey works like WISE. In addition, it will bring confirmation of the technical readiness and scientific value of several aspects for future mid-IR instrumentation at Extremely Large Telescopes. We also present several lessons learned during the project.

Showing 5 of 7 publications

SPIE Conference Volume | 7 September 2022

Optical and Infrared Interferometry and Imaging VIII

Conference Committee Involvement (2)

Optical and Infrared Interferometry and Imaging IX

17 June 2024 | Yokohama, Japan

Optical and Infrared Interferometry and Imaging VIII

17 July 2022 | Montréal, Québec, Canada

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