Abstract
Observation of radiation reflected, scattered or emitted in various regions of the electromagnetic spectrum can yield information about the structure of a planetary atmosphere. Instrumentation for the measurement of temperature, density, and composition and for cloud imaging is described, methods of information retrieval from radiometric observations are discussed, and some of the results for the atmospheres of Earth, Mars and Venus are presented. Further developments are considered particularly in the light of the information required for computer models of the atmosphere and for the consideration of the possible mechanisms for climatic change. A selection of references for further reading is included.