This book is a collection of the lectures, held at the International Summer School ISSAOS-2000 in L’Aquila (Italy), given by invited lecturers coming from both Europe and the USA. The goal of the book is to provide a broad panorama of spaceborne remote sensing techniques, at both microwave and visible-infrared bands and by both active and passive sensors, for the retrieval of atmospheric and oceanic parameters. A significant emphasis is given to the physical modeling background, instrument potential and limitations, inversion methods and applications. Topics on international remote sensing programs and assimilation techniques into numerical weather forecast models are also touched. The main purpose of the book is to offer to young scientists, Ph.D. or equivalent students, and to all who would like to have a broad-spectrum understanding of spaceborne remote sensing capabilities, introductory material to each remote sensing topic written by the most qualified experts in the field.