Optical Design & Image Reconstruction:Activities in Astronomical Imaging
In the field of astronomy, we carry out both instrumental developments and propose new approaches to process astronomical images.
The collaboration with the National Observatory of Thailand (NARIT), initiated in 2014, has led to the creation of an optics and photonics laboratory co-directed by one of us. The current flagship project is a coronagraph (EvWaCo) intended for the research and study of extrasolar planets and stellar environments. It is based on evanescent waves, with three unique properties compared to many competing projects: it is achromatic, it preserves the star path, and the mask size is variable [Alagao et al, 2021].
We are also working with the Thai Space Consortium, on the design of a hyperspectral imager, which will be Thailand's first satellite when it is launched in 2027 by China [Wanajaroen et al. 2022], [Wanajaroen et al. 2024].
The hypertescope is another example of the innovative instrumental concepts to which we have contributed with Pr Labeyrie [Xie et al. 2020].
On the data science front, we have developed inversion methods for multi-spectral reconstruction based on fine instrumental modeling and clever numerical optimization strategies [Berdeu et al. 2020], [Thé et al. 2023]. In Olivier Flasseur's Ph.D. thesis, we proposed exoplanet detection techniques [Flasseur et al. 2020a], [Flasseur et al. 2020b], see figure below, that we then extended to circumstellar disk reconstruction [Flasseur et al. 2021], [Flasseur et al. 2024], based on a non-stationary model of space-spectral correlations. Performance gains for exoplanet detection and characterization (x4 detection sensitivity, reduced photometric biases, improved astrometry) have been of great interest to the astrophysics community, and has led us to coordinate a project on the development of AI methods for the analysis of astronomical observations of exoplanets within the framework of PEPR ORIGINS.
We developed a general framework to better detect and characterize exoplanets from high-contrast observations. Our approach models spatial and spectral covariances.
Publications illustrative of our scientific activity :
[Alagao et al. 2021] Mary Angelie Alagao, Adithep Kawinkij, Christophe Buisset, Apirat Prasit, Thierry Lépine, et al.. Deep Contrast and Companion Detection Using the EvWaCo Test Bed Equipped with an Achromatic Focal Plane Mask and an Adjustable Inner Working Angle. The Astronomical Journal, 2021, 161 (5), pp.208. DOI Preprint
[Wanajaroen et al. 2022] Weerapot Wanajaroen, Christophe Buisset, Thierry Lépine, Pearachad Chartsiriwattana, Merisa Kosiyakul, et al.. TSC-1 Optical Payload Hyperspectral Imager Preliminary Design and Performance Estimation. Photonics, 2022, 9 (11), pp.865. DOI Preprint
[Wanajaroen et al. 2024] Wanajaroen, W., Lepine, T., Chartsiriwattana, P., Wannawichian, S., Rujopakarn, W., Poshyachinda, S., & Soonthornthum, B. , TSC-1 Offner Spectrometer Prototype Characterization. Photonics, 2024, 11 (7), p. 644. DOI
[Xie et al. 2020] Zongliang Xie, Thierry Lepine, Thomas Houllier, Haotong Ma, Denis Mourard, et al.. Hypertelescope with multiplexed fields of view. Optics Letters, 2020, 45 (7), pp.1878. DOI Preprint
[Berdeu et al. 2020] Anthony Berdeu, Ferréol Soulez, Loïc Denis, Maud Langlois, Éric Thiébaut. PIC: a data reduction algorithm for integral field spectrographs. Astronomy & Astrophysics - A&A, 2020, 635, pp.A90. DOI Preprint
[Thé et al. 2023] S. Thé, É. Thiébaut, L. Denis, T. Wanner, R. Thiébaut, et al.. Characterization of stellar companions from high-contrast long-slit spectroscopy data. The EXtraction Of SPEctrum of COmpanion (Exospeco) algorithm. Astronomy & Astrophysics - A&A, 2023, 678. DOI. Preprint
[Flasseur et al. 2020a] Olivier Flasseur, Loïc Denis, Éric Thiébaut, Maud Langlois. PACO ASDI: an algorithm for exoplanet detection and characterization in direct imaging with integral field spectrographs. Astronomy & Astrophysics - A&A, 2020, 637, pp.A9. DOI Preprint
[Flasseur et al. 2020b] O. Flasseur, Loïc Denis, E. Thiébaut, M. Langlois. Robustness to bad frames in angular differential imaging: a local weighting approach. Astronomy & Astrophysics - A&A, 2020, 634, pp.A2. DOI Preprint
[Flasseur et al. 2021] O. Flasseur, S. Thé, L. Denis, E. Thiébaut, M. Langlois. REXPACO: An algorithm for high contrast reconstruction of the circumstellar environment by angular differential imaging. Astronomy & Astrophysics - A&A, 2021, 651, pp.A62. DOI. Preprint
[Flasseur et al. 2024] Flasseur, O., Denis, L., Thiébaut, É., & Langlois, M. REXPACO ASDI: Joint unmixing and deconvolution of the circumstellar environment by angular and spectral differential imaging. Monthly Notices of the Royal Astronomical Society, 2024, 535(1), 689-728. DOI Preprint