The preceding chapters of this book have taken the remote sensing data model introduced in Chapter 1 and explored the observable spectral information content for materials, and the way in which this material is transferred to the input of the sensor in the form of pupil-plane spectral radiance. At this point, we can turn our attention to sensor instrumentation, in this case, imaging spectrometry. Before doing so, however, we will take a slight diversion in this chapter to overview the principles of conventional EO/IR imaging sensors, major sensor components, and metrics and methods for characterizing sensor system performance. For the reader familiar with EO/IR imaging sensor technology, this chapter can serve as a useful refresher; for the unfamiliar reader, it can serve as a tutorial. For both, it will provide a launching point from which to address the design and performance of the imaging spectrometers described in the subsequent three chapters. Some familiarity with the basic principles of geometrical optics (Smith, 1990) and Fourier optics (Goodman, 1996) is assumed in the treatments provided. For more details on these topics, the reader is encouraged to consult references provided at the end of this chapter such as Pedrotti and Pedrotti (1987) and Goodman (1985).
6.1 Remote Imaging Systems
Generically, a remote imaging system consists of the six major subsystems depicted in Fig. 6.1: imaging optics, focal plane array (FPA), readout electronics, data processing, pointing and stabilization, and calibration system. The imaging optics capture incident radiation and focus it onto the FPA so that there is correspondence between FPA image position and incident field angle or object position. From a radiometric perspective, the optics map the incident radiance from a scene position into the focal plane irradiance at the corresponding focal plane position. The FPA usually consists of an array of detectors, each of which converts the incident irradiance into a detected electrical signal, such as current or voltage.