An international scientific research program, called Mission to Planet Earth, is being planned as a 25-year effort. It will use a new, integrated network of Earth satellites to understand at last how the atmosphere, seas, and living creatures function together as a single global system. Mission to Planet Earth will include three groups of satellites carrying a broad array of remote sensing instruments. Satellites in polar orbit will scan the Earth as it turns beneath. Those in geosynchronous orbit, fixed in position relative to the Earth, will stare at limited areas. Earth probes in equatorial orbit will study ozone, rainfall, and oceanic biology. Data from these satellites, which will include detailed measurements and information about climate and weather, land, crops, ocean temperatures and currents, will be fed to ground-based computers for analysis by scientists. These data are expected to provide a more detailed and accurate picture of the evolving climate and ecosphere than is now possible with the fragmentary measurements from existing satellites and ground stations.