Potentials for high-resolution imaging with small satellites

In the field of space-borne topographic mapping instruments the trend to smaller ground sample distances (GSD) can be observed, making use of the best technology available at the given time. From the 80 m GSD of ERTS (later renamed Landsat-1), the first satellite dedicated to civil space-borne Earth surface imaging launched in 1972, the GSD now approaches 1 m. Mass and power consumption of spacecraft and instruments follow similar trends. Alternatives to passive optical systems such as SAR and laser altimeters also benefit from the immense improvement in very diverse fields of technology. Nevertheless, the most promising prospects for topographic mapping with small satellites are connected with passive optical systems, especially push-broom systems. The paper tries to contribute to the answer of the question, how far can we go with decreasing instrument size, mass and power consumption, and decreasing the GSD at the same time. After explaining the basic topographic mapping concepts, the paper deals with important parameters for mapping with small satellites: spatial resolution, radiometry, mass, volume, power consumption, microelectronics, pointing accuracy and stability, data volume and transmission. From the technology point of view, small satellite missions for topographic mapping are feasible. One system is already in Earth orbit, others are in the planning stage. There is a good chance to install mapping systems with a low cost space segment. It is a question of market requirement and behavior whether or not these small satellite based mapping systems can successfully compete with existing space-borne or airborne based mapping systems.