Inverse problems in space remote sensing: A sensitivity study on the atmospheres of Earth-like exoplanets

Abstract

More than one thousand exoplanets have been discovered in the past two decades, with some dozen of them in the host stars’ habitable zone and with size and mass similar to Earth. Furthermore, spectra of exoplanets become available with reasonable quality (resolution and noise) that trigger the question of remote sensing of the planet’s atmosphere. The objective of this sensitivity study is to identify the optimal state vector representing the atmosphere in the inverse problem. Solving the inverse problem will ultimately allow to characterize the planet and determine its habitability. Using a high resolution infrared radiative transfer code with a line-by-line molecular absorption model, we calculate synthetic spectra of exoplanets orbiting dwarf stars. Key parameters describing the atmosphere (i.e., molecular abundances, temperature, pressure) are identified and the Jacobians (i.e. partial derivatives of the spectra) are evaluated to investigate the feasibility to retrieve the state of the planetary atmosphere.