ABSTRACT
This chapter deals with active remote sensing by laser. The myriad of modern applications for lasers includes the remote sensing and investigation of distant objects. The principle of laser radar is of course very simple and straightforward. The available laser beam sizes and speckle effects of laser radiation are of course determined by well-established principles of optical propagation. An advanced optical air data system (OADS) for measurements high in the atmosphere was built and flown in the early 1990s. The laser beam is sent out from an optical transmitter towards the object of interest, often referred to as the "target". The scattering of light from the target is of course fundamental to the technique and has many possible forms. Differential absorption, fluorescence and surface heating/vaporization are generally specific to the target and may be used with an appropriate choice of laser wavelengths to provide chemical-type information.
