FUNDAMENTALS OF REMOTE SENSING FOR RISKS ASSESSMENT FRANÇOIS BECKER International Space University and University Louis Pasteur, Strasbourg, France; E-mail: becker@isu.isunet.edu Abstract. Remote sensing instruments aboard satellites observe the properties (e.g., intensity) of electromagnetic radiation (e.g., from the Sun) backscattered and/or emitted by the surface. Thus, they record some information about the surface. Different information is obtained in the visible/near infrared, thermal infrared and microwave parts of the spectrum. 1. Introduction As has been stated in the previous paper (Rycroft, 2000), environmental risk as- sessment is a very important task. Indicators of environmental risks which are reliable and measurable must be identified. These indicators must be measured and monitored in a reliable manner at an affordable cost, to estimate the risks and to locate the potential risks with a reliable probability of occurrence. Remote sensing may be a very useful tool to contribute to the achievement of these tasks. In fact, remote sensing allows a continuous monitoring of all the areas where environmental risks may occur, leading to the possibility of implementing warning systems. As an example, considering tornadoes in meteorology, the indic- ators could be the temperature and structure of the clouds, and their trajectory and velocity. These indicators can be monitored by remote sensing using radiometry from geostationary satellites which allow a global view every half an hour and, very soon, a quarter of an hour, by Meteosat Second Generation (MSG), and even shorter when focussed on a particular tornado, as is done by GOES. The aim of the STER course is to make risk managers aware of the potentialities of remote sensing and to give them the basic tools to identify the most relevant indicators which are measurable and which can be monitored by remote sensing. The course presents how remote sensing works, what can be measured by remote sensing, how to interpret and analyse the recorded data, and what are the constraints in the choice of an indicator measurable by remote sensing. In Section 2, we review the definition and principles of remote sensing; we shall introduce what can be called the remote sensing chain, with its components. Section 2 also introduces the characteristics of the electromagnetic radiation. Once the elements of the remote sensing set-up have been presented, we can consider the flow of information from the ground to the instrument, and the transformation of this information into data by the instruments. Different parameters come into play; Surveys in Geophysics 21: 127–131, 2000. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.