Artist’s rendition of the Upper AtmosphereResearch Satellite (UARS) superimposed on asunrise view of the Atlantic Ocean off thecoast of Jacksonville, Florida on February 23,2003. NASA’s UARS satellite is one of 48 dif-ferent international Earth-observing satellitesused throughout this book. It was deployedfrom Space Shuttle Discovery on September14, 1991 and raised to an orbital altitude of 600km where it provided observations of theEarth’s atmospheric chemical compositionuntil the end of 2005, circling the globe forover 5000 days. (Photograph from theInternational Space Station, NASA imagenumber ISS006-E-32544.)