Unmanned satellites have now been used for almost a decade in useful earth-oriented applications; communication, navigation, geodetic survey, meteorology.In the coming 1970-1980 era, these applications are expected to increase in number and expand in scope; and to be augmented by additional applications having to do with the discovery and monitoring of the earth's natural resources, and of other phenomena of interest to man -- disasters, patterns of cultural development, oceanic traffic, and others.These latter tasks fall within the functional category of “observation” tasks wherein the principal role of a space system will be the collection of information, both by direct observation and by gathering data emitted from sensors deployed over the earth's surface. Eventually, these observation functions will be complemented by satellite-directed surface activity -- ships, aircraft, land vehicles. In this later era, the role of the satellite will be expanded from that of pure observation to that of observation combined with elements of command and control.In this observation role, the satellite will serve the needs of mankind at large, channeled through specific categories of “users”. These “users”, which represent specific disciplines, are embodied by special government agencies such as USDA, or by private concerns interested in specialized aspects of resource exploitation.It is the purpose of this paper to present an overview of the role of such satellite systems.* To this end, it is first necessary to lay down realistic user requirements, namely, the kind of things the “users” wish to see accomplished and the descriptive parameters thereof, including: precision of observation (resolution); dimensionality of observation (spectral band or color); size of observed dimension (areal coverage); required frequency of observation; location of the phenomena to be observed, and others describing where, when, how often, and how accurate the user wishes the observation to occur.Subsequently, an overview is offered of the observation sensors which will be practically available during the time frame under consideration. Finally, the sensor capabilities are matched with the user requirements, with due regard for minimization of sensory payload by means of commonality analysis, to determine to what extent such observation satellites are practical, and if so, what are their major characteristics.Next, the optimal orbital elements for such satellites are discussed.