FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) is a satellite mission selected in 2019 as the ninth ESA (European Space Agency) Earth Explorer mission. FORUM will provide interferometric measurements in the spectral interval encompassing the Far-InfraRed (FIR) part of the spectrum, responsible for about 50% of the outgoing longwave ux lost by our planet into space. While existing
instruments are unable to measure the Top of the Atmosphere (TOA) resolved spectrum in the FIR, more accurate measurements may reduce the uncertainties in estimating the Earth's warning. The observations will also improve the knowledge of several atmospheric variables, such as tropospheric water vapor, ice cloud properties and land emissivity in the FIR. In the early stages of the mission development, an End-to-End Simulator (E2ES) has been devised to demonstrate proof-of-concept and to evaluate the impact of
instrument characteristics and scene conditions on the accuracy of the reconstructed atmospheric properties. The retrieval is obtained through inversion of the radiative transfer equation. In the retrieval step,
performed in the E2ES by the CLAIM (CLouds and Atmosphere Inversion Module) code, the atmospheric state that best reconstructs the simulated measured spectrum is determined. The inversion is a severely ill-conditioned problem, and is solved using a Gauss-Newton (GN) method combined with the Optimal Estimation (OE) approach, a Tikhonov regularization scheme based on a standard Bayesian approach. The retrieved profiles may present unphysical oscillations, requiring the application of the Iterative Variable Strength regularization (IVS) after the convergence of the GN method. In this seminar, I will focus on the retrieval of the surface emissivity, in particular on the choice of the retrieval grid step and the IVS parameters, using the FORUM simulated measurements in di erent latitude bands.
Cristina Sgattoni obtained her PhD in Mathematics at the University of Florence in 2020. During her PhD, she worked on numerical optimization with a particular focus on spectral residual methods for solving nonlinear systems of equations. She applied her research to rolling contact problems in collaboration with the Industrial Engineering department at the University of Florence. In 2021, Cristina won the
competitive research fellowship at the Institute of Applied Mathematics (IAC) of the National Research Council (CNR) in Florence, where she currently works as a postdoctoral researcher. Speci cally, she works
on the development of numerical methods for remote sensing and radiative transfer inversion. She is involved in the preparatory phases of the European Space Agency satellite mission called FORUM whose
aim is to provide the rst high spectral resolution measurements from space in the far infrared part of the electromagnetic spectrum. Cristina's research is supported by the Italian Space Agency (ASI) and the
European Space Agency (ESA).
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