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GEM: Geospace Environment Modeling



Shortly after the beginning of the “space age” with the launching of the first man made object into terrestrial orbit, geospace assumed a fundamental role as a technological resource for all countries, advanced and developing alike. Today, satellite systems for communications, weather prediction, navigation, and remote sensing of natural resources are supporting, in an essential way, many facets of societal operations. We must expect that this trend will continue; for instance, in perhaps less than 3 decades, transatmospheric transportation will be routine and satellite systems will sustain human colonies in space.

The medium in which Earth-orbiting systems operate is hostile. Far from a perfect vacuum, it is made up of high-temperature gas and corpuscular radiation of varying densities and intensities; these solar-activity controlled variations can reach proportions dangerous to orbital stability, to electronic systems performance, to shuttle and spaceplane reentry, and to the life of humans in orbit. Dramatic examples of solar-activity-induced satellite failures are the unexpected early degradation of the orbit of Skylab due to unusual upper atmosphere heating and the demise of satellite GOES-5, most probably caused by a large injection of energetic electrons from the outer magnetoshere. The need to predict “weather and climate” in geospace is becoming as important as the need to predict weather and climate in the inhospitable regions on Earth into which industrial activity has moved during the last decades, such as the Arctic and some of the arid lands.

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