The largest and most expensive satellite ever built by Europe blasted off today, beginning its mission to monitor the environmental health of Planet Earth. The environmental satellite, or Envisat, was launched from French Guiana into orbit about 500 miles above the surface of the Earth, where it will circle the planet every 100 minutes. Envisat’s mission is to collect vital data on how Earth’s land, oceans, ice caps, and atmosphere are changing. The information will be analyzed by scientists and used to help establish European environmental policy. The program’s sponsors called it a powerful symbol of the strength of a united Europe, and Jose Achache, director of the Earth Observation program for the European Space Agency, said the mission would enable scientists and environmentalists “to trace the smallest changes to the Earth’s surface anywhere on the globe.”

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