Upper Atmosphere Research Satellite

Instruments

CLAES was a spectrometer that determined concentrations and distributions of nitrogen and chlorine compounds, ozone, water vapor and methane, producing the first global maps of ozone-depleting chlorinated compounds. It inferred gas amounts by measuring unique infrared signatures, requiring high resolution and sensitivity achieved by combining a telescope with an infrared spectrometer. The instrument was cryogenically cooled with an inner tank of solid neon at −257 °C and an outer tank of solid carbon dioxide at −150 °C; the cryogens evaporated on May 5, 1993, ending its useful life after 19 months.

CLAES looked sideways through the stratosphere and lower mesosphere, creating a global database of vertical distributions of ozone-layer gases and their variations. ISAMS was an infrared radiometer measuring thermal emission from Earth's limb on both sides of the spacecraft, using pressure-modulation for high spectral resolution and stirling-cycle coolers for detector sensitivity. It employed 7 gas cells for CO2 (two cells), CO, CH4, N2O, NO2, and H2O, with the CO2 cells also enabling measurement of ozone, nitric acid, and dinitrogen pentoxide.

End of mission and re-entry

UARS was decommissioned on 14 December 2005 after final perigee lowering burns reduced its orbit to 518 km by 381 km, followed by passivation of systems. On 26 October 2010, the International Space Station performed a debris-avoidance maneuver due to a conjunction with UARS.

NASA announced the impending uncontrolled re-entry on 7 September 2011, noting a small potential risk to the public. By 23 September 2011, the orbit had reduced to 175 by 185 km, with 26 pieces of debris expected to survive, the largest at 158.30 kg possibly reaching the surface at 44 m/s and smaller pieces at up to 107 m/s. At 07:46 UTC on 24 September 2011, NASA stated the satellite penetrated the atmosphere over the Pacific Ocean.

The Joint Space Operations Center later announced the reentry occurred at 04:00 UTC on 24 September just downrange of American Samoa, with a debris field extending 300 to 800 mi northeast.