ABSTRACT
This chapter discusses the infrared (IR) systems covering a wide gamut of space-based surveillance applications. Although the basic range equation has been designed for scanning sensors, it can also be used for several classes of staring sensor systems with suitable changes in some of the system parameters. The detectors universally used in high-performance IR search systems basically respond to the quantum flux input, that is, the number of photons per second input, the radiant flux. Photoconducting, photovoltaic, and other quantum detectors usually respond nearly uniformly to the quantum flux over a broad spectral region. Beyond their long-wavelength cutoff, their response falls rapidly. Analyses in which the inputs are measured in terms of quantum flux rather than radiant flux are simplified in many cases, and difficulties with the concept of effective watts are avoided. The range performance of a system is established by its limiting noise.
