Infrared multiscale sea surface modeling Karine Caillault a1 , Sandrine Fauqueux a , Christophe Bourlier b , Pierre Simoneau a a ONERA, Applied and Theoretical Optics Department, Chemin de la Hunière, 91761 Palaiseau Cedex, France b IREENA, Ecole polytechnique de l'université de Nantes, rue Christian Pauc, La Chantrerie, BP 50609, 44306 Nantes Cedex 3, France ABSTRACT An analytical model of infrared sea surface optical properties is developed to access to statistical radiative characteristics of a wind-roughened water surface. Any surface size, i.e. that contains or not all the statistical information of the stochastic process governing the sea surface, can be considered. This model deals with the problem of multi-resolution in a sensor field of view. Model validation has been conducted in 1D by comparison with a reference code and in 2D by comparisons with optical properties measurements and with validated 1D cross sections. Keywords: rough surface, infrared sea surface optical properties, multi-scale. 1. INTRODUCTION Assessment of optronic systems performances implies to adapt background signatures models to new optical sensors. Modeling of background radiation requires to take into account both high spatial variability of optical properties and larger scale variability. Moreover, multi-scale approaches have to be developed in order to fulfill the requirement in computing images of any observational configurations (nadir or grazing view geometry from ground-based, airborne or shipborne sensors), i.e. introducing multi-resolution in the field of view. In the scope of the development of a new version of the infrared background scene generator MATISSE 1 (Modeling of the Earth for the Imaging and the Simulation of the Scenes and their Environment), a model of sea surface optical properties will be implemented. It introduces a 1-meter scale spatial variability on background and sub-pixel variability is included. Local characteristics, such as waves from swell to capillarity waves, and associated atmospheric conditions (wind, fetch) are taken into account. The spectral bandwidth ranges from 765 to 3300 cm-1 (3 to 13 μm). Our model is based on recent works 2,3,4,5 devoted to the statistical radiative characteristics of a wind-roughened water surface, assuming surface average is flat. The aim of our study is to give analytical expressions of sea surface optical properties for any slopes mean and variance, and for any resolution required by the observational configuration, answering the problem of multi-resolution in the field of view. We address firstly one-dimensional shape of the sea surface to perform a proper validation by comparison with a reference code. This model, requiring a very thin discretization of the sea surface, is very time consuming and cannot be used in the 2D case. So in a second step, 2D optical properties are calculated along a surface cross-section and compared with 1D optical properties previously validated. 1 karine.caillault@onera.fr