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the perspective available from space we simply cannot adequately monitor, much less characterize, the dynamic process of our planet.

Space exploration revolutionized our perception and understanding of our planet. In the late 1960s, the Apollo program provided people around the world with a new perspective of the Earth, and created the awareness that our planet is a fragile place. The space program has continued to contribute to the understanding of our home planet, but our understanding is far from complete. In the last two decades, scientists have learned that the earth is a synergistic system, and it must be studied as a system. AS this Committee has heard, the oceans, atmosphere, continents, and biosphere, are highly interactive. None can be understood in isolation. Further, changes in one can reverberate through the system and have influence on a global scale. 

Scientists have also learned that human civilization's activities over the last several decades have begun to affect the conditions on the planet. We are an active and influential component of the system. If we are to avoid being a destructive force, we must understand the consequences of our actions. 

We do not yet understand how our planet works. Current models of the earth system are not good enough. We need better, more comprehensive, observations to enhance our understanding of all of earth's processes. With that improved understanding, scientists can formulate computer models which better describe, and perhaps eventually predict, the changes that are observed to occur on all timescales. Although ground-based measurements are essential, they provide only pieces of the story. To unravel the complex tangle of interacting physical, chemical, and biological processes, we have to mount a concerted effort to study them from space.

In the 1987 report "Leadership: America's Future in Space", Mission to Planet Earth was described as "an initiative to understand our home planet, how different forces shape and affect its environment,

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