EARTH OBSERVATIONS IN THE TWENTY-FIRST CENTURY.

Some of the achievements of Earth observations from past space missions are described. Also discussed are the achievements to be anticipated from currently approved and planned Earth observation missions. In looking forward to what we expect the objectives of Earth observations from space to be in the future, together with what we anticipate technology to enable, we discuss what the Earth observing program will look like during the first part of the twenty-first century. It is concluded that a key part of this program will be long-term observations from unmanned polar orbiting platforms holistically viewing the Earth system.