Optical remote sensing of the earth from aircraft and from orbit has made unique contributions to understanding the dynamics of the atmosphere, oceans, and the vegetation cover of the land, as well as provided new perspectives in the study of the solid earth. This paper encompasses optical remote sensing of the earth's surface in the region of 0.4 to 15 µm and is divided into four areas: principles, applications to science disciplines, recent sensor history, and new technology developments. The latter developments promise to revolutionize the methods used and the types of problems addressed with remote sensing techniques.