A major NASA initiative to develop state-of-the-art remote sensing instruments for global studies of the land surface, biosphere, solid earth, atmosphere, and oceans. Current plans call for three major satellite platforms, two in polar and one in a low inclination orbit. One polar orbiter (EOS-AM) will have a midmorning descending node crossing time, while the other (EOS-PM) will have an equator crossing time in the afternoon. The third (EOS- CHEM) will be in a low inclination orbit. Each EOS satellite is designed to make maximum use of simultaneous, complementary views of the earth from a wide variety of instruments. EOS-AM will be the first satellite launched in this series, followed by EOS-PM, and the EOS Chemistry Mission (EOS-CHEM). The AM mission will be based on a suite of instruments including an advanced spaceborne thermal emission and reflection radiometer, a cloud and earth radiant energy system, a multiangle imaging spectroradiometer, a moderate resolution spectroradiometer, and a sensor to measure pollution in the troposphere. Instruments carried on the PM platform will include the advanced microwave scanning radiometer-EOS, the moderate resolution spectroradiometer, an advanced microwave sounding unit, an atmospheric infrared sounder, a humidity sounder for Brazil, and the cloud and earth radiant energy system. The EOS-CHEM will monitor atmospheric ozone, aerosols, and pollution using the high-resolution dynamics limb sounder, the microwave limb sounder, an ozone monitoring instrument, and the tropospheric emission spectrometer.