Observatoire de Paris Institut national de recherche scientifique français Univerité Pierre et Marie Curie Université Paris Diderot - Paris 7

  • Lundi 10 octobre 2022 à 16h00 (Salle de conférence du bâtiment 17)

    A year of near-IR spectroscopy on Mars with Perseverance/SuperCam

    Clément Royer et Lucia Mandon (LESIA)

    The Perseverance rover (Mars 2020 mission, NASA) landed in Jezero crater, Mars, the site of an ancient lake, on February 2021. The main science objectives of the mission are the characterization of past environments, the search for preserved biosignatures and the collection of samples to be returned to Earth by the MSR mission (Mars Sample Return). The payload of Perseverance includes the SuperCam instrument, which combines various remote-sensing techniques to investigate the elemental and mineralogical composition of rocks and soils. In particular, the near-infrared reflectance spectrometer (IRS), which covers the 1.3–2.6 µm range, allows for the identification of a wide variety of mineral phases, and especially hydrated ones.

    From a technical point of view, IRS is a miniaturized spectrometer based on AOTF (Acousto-Optic Tunable Filter) technology. This optical element is the cornerstone of the IRS’ performance and its flight calibration will be presented in this seminar. Then, we will give an overview of the minerals detected by the IRS during the first year of the mission and the implications on the geological history of the crater floor in terms of igneous and alteration processes. As the IRS is the first near-infrared spectrometer operating directly on the surface of Mars, we will also discuss how these results bring insights into the orbital studies using near-infrared data.

  • Lundi 3 octobre 2022 à 16h00 (Salle de conférence du bâtiment 17)

    The Dragonfly landing site seen by the Cassini RADAR

    Léa Bonnefoy (Cornell University)

    The Selk crater region is the future landing site of NASA’s Dragonfly mission to Titan. The region was imaged by the Cassini RADAR at incidence angles from 5° to 72° and at various polarization angles. Using this data set, we assembled backscatter curves for six terrains. By fitting different models to these data we derived new composition and roughness constraints for each terrain. Topography from radarclinometry also revealed a non-uniform crater rim, less eroded than previously thought.

  • Jeudi 29 septembre 2022 à 16h00 (Salle de réunion du bâtiment 16 et visioconférence)

    Data reduction and inverse problem approaches - An efficient (and cheap) way to push the instrumental limits

    Anthony BERDEU (LESIA)

    Study of astrophysical objects requires always more complex models (black hole surrounding, exoplanet atmosphere, accretion disk, galaxy formation and evolution, …) whose inputs imply always more precise measurements. On the other side, the astronomical instruments start to reach their fundamental limits (negligible sensor readout noise, precise mirror polishing, technologies harder to scale up to extremely large telescopes, …). During my talk, I will discuss how data science applied for optimal data reduction and processing via inverse problem approaches can bridge this gap, by pushing the experimental limits without the need of further instrumental developments. I will introduce different applications of my research : integral field spectroscopy (SPHERE/IFS), blind deconvolution and PSF reconstruction (SPHERE/ZIMPOL) and extreme adaptative optics for coronagraph (Evanescent Wave Coronagraph, EvWaCo).