Geostationary satellites are shown to play an essential role in monitoring climate change. The orbits of these satellites are unique in their ability to provide measurements of the same location at frequent intervals of time (e.g. every 15 minutes), in comparison with those from polar-orbiting satellites (every 12-hours). The importance of frequent measurements for monitoring climate will be explained.

General requirements for making climate quality observations from the geostationary platform will be discussed first, followed by more specific requirements. General requirements include overlapping satellites in time, minimization of orbit drift, rigorous pre-launch characterization of instruments, and adequate on-board calibration. Specific requirements refer to what geophysical parameters should be measured and what should be their attributes. Special emphasis is given to the most important attributes, accuracy and drift. An explanation will be given as to how the required accuracies and drifts were determined and whether these can be achieved. Finally, a brief schedule of major events leading to the launch of the next series of GOES (Geostationary Operational Environmental Satellites) will be presented.