Introduction

In this chapter we consider aircraft and satellites as platforms for remote sensing. There are other, less commonly used, means of holding a sensor aloft, for examples towers, balloons, model aircraft and kites, but we will not discuss these. The reason for this, apart from their comparative infrequency of use, is that most remote sensing systems make direct or indirect use of the relative motion of the sensor and the target, and this is more easily controllable or predictable in the case of aircraft and spacecraft. Figure 10.1 shows schematically the range of platforms, and their corresponding altitudes above the Earth's surface.

The spatial and temporal scales of the phenomenon to be studied will influence the observing strategy to be employed, and this in turn will affect the choice of operational parameters in the case of an airborne observation or of the orbital parameters in the case of a spaceborne observation.

Aircraft

Aircraft of various types provide exceptionally convenient and operationally flexible platforms for remote sensing, carrying payloads ranging from a few tens of kilograms to many tonnes. With a suitable choice of vehicle, a range of altitudes can be covered from a few tens of metres, where atmospheric propagation effects are negligible, to many thousands of metres, above most of the Earth's atmosphere. The choice of flying altitude will obviously have an impact on the scale, spatial coverage and spatial resolution of the data collected.