Information content of the radiative transfer theory

ABSTRACT The new generation of instruments to measure the atmosphere gives a large amount of information whose contentis not immediately obvious. For this reason the information content (in the Shannon sense) and the number ofdegrees of freedom for signal related to parameters to retrieve, are crucial to carry out, for instance, the selectionof microwindows or subset of channels for retrieval. This seems to be even true for the miniaturized devices likethose obtained by MEOMS technologies that have high flexibility because are highly integrated. In this paperwe present the methodologies to obtain the information content related to wavelengths selection from satellitewith limb and nadir view with in mind the MEOMS technology.Keywords: Information content, remote sounding, spectroscopy, atmosphere, aerosol retrieval 1. INTRODUCTION Remote sensing measurements have intrinsic limitations due to their complexity (Guzzi and Smokty' ) . The mat-ter has also been introduced by different authors (among those we cite Twomey,2 Rodgers3) by a regularisationand bayesian approach, as a function of the complexity of the problem to solve.A new generation of spectral instruments have introduced new analysis methods to retrieve the atmosphericparameters. In the near future a dramatic improvement of spectroscopic instruments will be obtained by theintroduction of MEOMS (Micro-Electro-Optical-Machining System) technologies. Such technologies, not onlywill reduce the size of the instruments integrating the optics with the sensors, but will offer high flexibility andability to build up intelligent devices.In our laboratories are under developing small Mach-Zehnder interferometers and a small imager interferom-eter is under assembling as it will briefly described in the next paragraph. These instruments offer a very largespectrum of applications: from medical to space.