UARS

UARS carried instruments including the Microwave Limb Sounder (MLS) and the Halogen Occultation Experiment (HALOE) that provided the first comprehensive measurements of stratospheric ozone chemistry. The satellite tracked ozone-destroying chemicals like chlorofluorocarbons (CFCs) and confirmed that human-made chemicals were causing the Antarctic ozone hole. UARS data helped verify the effectiveness of the Montreal Protocol, the 1987 treaty that phased out ozone-depleting substances.

UARS re-entered Earth's atmosphere on September 24, 2011, after NASA deliberately lowered the satellite's orbit following decommissioning in 2005. The 5,900-kilogram satellite broke up during re-entry, with surviving debris reportedly falling into the Pacific Ocean. NASA calculated the risk of human injury from falling debris as approximately 1 in 3,200, which was higher than typical re-entry risk thresholds.

UARS was deployed from Space Shuttle Discovery during the STS-48 mission in September 1991. The satellite was released by the shuttle's robotic arm operated by astronaut Mark Brown. STS-48 crew members also included Commander John Creighton and included a separate spacewalk unrelated to UARS deployment.

UARS operated for approximately 14 years, far exceeding its planned 3-year mission lifetime. The satellite was launched in September 1991 and continued providing atmospheric science data until 2005 when NASA decommissioned it. Several instruments, including the Cryogenic Limb Array Etalon Spectrometer (CLAES), stopped working earlier due to coolant depletion, but others functioned throughout most of the satellite's life.