EARTH OBSERVING SYSTEM AM1 MISSION TO EARTH

In 1998, NASA launches EOS-AM1, the first of a series of the Earth Obs erving System (EOS) satellites. EOS will monitor the evolution of the state of the earth for 18 years, starting with the morning observation s of EOS-AM1 (10:30 a.m. equatorial crossing time). An integrated view of the earth, as planned by EOS, is needed to study the interchange o f energy, moisture, and carbon between the lands, oceans, and atmosphe re. The launch of EOS-AM1 and other international satellites marks a n ew phase of climate and global change research. Both natural and anthr opogenic climate change have been studied for more than a century. It is now recognized that processes that vary rapidly in time and space-e .g, aerosol, clouds, land use, and exchanges of energy and moisture-mu st be considered to adequately explain the temperature record and pred ict future climate change. Frequent measurements with adequate resolut ion, as only possible from spacecraft, are key tools in such an effort . The versatile and highly accurate EOS-AM1 data, together with previo us satellite records, as well as data from the Advanced Earth Observin g System (ADEOS) (I and II), Tropical Rainfall Measuring Mission (TRMM ), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Along Track Scanni ng Radiometer (ATSR), Medium Resolution Imaging Spectrometer (MERIS), Environmental Satellite (ENVISAT), EOS-PM1, Land Remote-Sensing Satell ite (Landsat), and ground-based networks is expected to revolutionize the way scientists look at climate change. This article introduces the EOS-AM1 mission and the special issue devoted to it. Following a brie f historical perspective for an insight into the purpose and objective s of the mission, we shall summarize the characteristics of the five i nstruments onboard EOS-AM1. Specifically, we concentrate on the innova tive elements of these five instruments and provide examples of the sc ience issues that require this type of data. These examples show the i mportance of collecting data simultaneously from each of the five EOS- AM1 sensors for studying rapidly varying processes and parameters.