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of proof for scientists is greater in the greenhouse warming problem than for ozone depletion because the consequences of dealing with the problem are so much greater; it is one thing to remove the CFCs from the economy, it is quite another to reduce fossil fuel consumption.

[Figures of UARS, Topex/Poseidon]

NASA currently has under construction three satellite projects which will provide important data on global change up until the time we can begin Mission to Planet Earth. The Upper Atmospheric Research Satellite (UARS) scheduled for launch in 1991 will provide definitive measurements of the chemistry and dynamics of the upper atmosphere and provide for a complete, global set of atmospheric data on the earth's ozone layer. Topex/Poseidon is a joint project with France to measure with great accuracy the height of the world's oceans, from which global ocean circulation can be inferred. It is scheduled for launch in 1992. The results from this mission has a strong relationship to those of the NASA Scatterometer, which has been selected (preliminarily) for flight on the Japanese ADEOS satellite in 1994, and which will measure wind stress on the ocean surface for determination of ocean currents. These projects address the coupling between the oceans and the atmosphere, which is key to understanding how the two principal systems of the earth's climate operate together.  

Each of these missions attacks a focused problem important to understanding our global environment. They do not, however, deal with the earth as an integrated system. We need to observe the component parts of the earth simultaneously to achieve an integrated understanding of how the atmosphere, ocean, ice and biosphere interact and operate as a system. These are the objectives of Mission to Planet Earth. 

The Architecture of Mission to Planet Earth

Now is the time for Mission to Planet Earth. Global changes in atmosphere and on the surface of the earth have already been observed, and the impact of these changes is uncertain. We now have the ability to observe the earth from space, and we have the technology and scientific expertise to tackle earth system science. There is a world-wide awareness of the problem of global change, and international and interagency cooperation is growing. There is a growing public awareness of changes in the global environment that demands attention, which creates the opportunity to demonstrate U.S. leadership in an area where every citizen of the world will ultimately benefit.

[Figure F243.001]

Mission to Planet Earth consists of four major types of space components: