The American Association for the Advancement of Science calls it a crisis. Atmospheric scientist Timothy L. Killeen, the president of the American Geophysical Union, says it "could harm our ability to protect our citizens." We call it plain old scary. It's the endangered future of our nation's arsenal of Earth-observing satellites, the 42 instruments that enable scientists to monitor the planet. Satellite images and colorful data sets like the ones on the following pages help researchers track killer hurricanes, plan conservation efforts, manage water resources, and predict glacial melting.
Yet our fleet is aging, and badly.