Remote sensing from satellites provides a unique tool to measure the parameters of the Earth on a worldwide scale. A number of organizations are currently engaged in, or proposing to embark on, worldwide measurement/monitoring programs. Program objectives vary in type and complexity, including a form of technical library and an ambitious experiment to validate algorithms to derive land surface climatological parameters. Modeling and understanding the Earth as an integrated system is an immense undertaking and will require at least as many measurements as currently acquired. Development of a long-term program of Earth system monitoring/modeling, such as the International Global Change Program proposed by the International Council of Scientific Unions, could provide the necessary focus and structure for effective international coordination and cooperation.