ABSTRACT
The objective of this chapter is to provide an overview of the basic aspects involved in the acquisition and in the production of remote sensing (RS) data. In this context the word sensor will be used as a synonym of acquisition system. The basic principles of RS and a denition of the physical entities involved in the acquisition process will be brie y recalled, by focusing on the main parameters of sensors, which determine the characteristics of the acquired images. Some aspects related to sensors will be explained, in order to understand the properties of the data that are encountered in RS applications. The goal is introducing the reader to basic concepts that are relevant for RS image fusion. Optical sensors are rst presented by making a distinction between re ected radiance and thermal imaging sensors. Afterward, such active sensors as synthetic aperture radar (SAR) and LiDAR are dealt with. Although LiDAR is an optical instrument, its importance lies in its feature of being active. When the various sensor typologies are presented, a brief review will be done of some imaging sensors that are relevant for pansharpening fusion. Their main characteristics are presented in order to delineate the framework of the past established work in image fusion and motivate the present and future research activity.
