Artist's impression of UARS

This conceptual image shows the Upper Atmosphere Research Satellite (UARS), launched on 15 September 1991 by the space shuttle Discovery. Originally designed for a three-year mission, UARS measured chemical compounds found in the ozone layer, wind and temperature in the stratosphere and the energy input from the Sun. Together, these measurements helped define the role of Earth's upper atmosphere in climate and climate variability. The 35-ft-long, 15-ft-diameter UARS was decommissioned on 14 December 2005 and underwent a destructive reentery during the night of 23/24 September 2011.