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The time series of light reflected from exoplanets by future direct imaging can provide spatial information with respect to the planetary surface.
Kawahara & Fujii (2010) proposed Spin–Orbit Tomography (SOT) to obtain the two-dimensional spatial distribution from the diurnal and seasonal variations in reflected light. We focused on two applications of SOT. First, Aizawa et al. (2020) obtained highly accurate spatial distribution maps by introducing sparse modeling to SOT. Second, Kawahara (2020) introduced spectral unmixing, a remote sensing method, to SOT. This method enables us to obtain the spatial distribution of the planet’s surface and the reflection spectrum from the luminosity variations at multiple wavelengths. In our study, we combined SOT, sparse modeling, and spectral unmixing. We placed sparsity-inducing constraints and reformulated the solution into an appropriate form to use the proximal gradient method, one of the optimization algorithms.
As a result, we obtain highly accurate and more sparse planetary surface distributions and reflection spectra. I will describe this method and show the results of tests using Earth data.
Atsuki Kuwata is currently a PhD student of Prof. Motohide Tamura’s group in the Department of Astronomy, the University of Tokyo.
His research focuses on global mapping of exoplanets, a theoretical study combining astronomy and informatics.
Video record: (IN-CAMPUS republic)
https://vshare.sjtu.edu.cn/play/32499def0f0e1f3496c023bb5c686325