UARS

UARS. The Upper Atmosphere Research Satellite was a major NASA Earth observation satellite mission dedicated to studying the stratosphere, mesosphere, and lower thermosphere. Launched in 1991 from the Kennedy Space Center, it provided critical long-term data on atmospheric chemistry, dynamics, and energy input. Its findings were fundamental to understanding ozone depletion, particularly the role of chlorofluorocarbons, and influenced major international agreements like the Montreal Protocol.

Overview

The spacecraft was a key component of NASA's Mission to Planet Earth, later known as the Earth Observing System. It operated in a sun-synchronous low Earth orbit, allowing its suite of instruments to measure atmospheric constituents across different times of day. The mission represented a significant collaboration between NASA's Goddard Space Flight Center, which managed the project, and the scientific community. Data from its instruments were processed and archived at the NASA Langley Research Center's Atmospheric Science Data Center.

Development and Launch

Development of the satellite began in the late 1970s, with General Electric serving as the prime contractor for the bus under the direction of NASA. The mission was designed to address growing scientific concern over the Antarctic ozone hole and broader changes in the upper atmosphere. It was launched on 12 September 1991 aboard the Space Shuttle Discovery during the STS-48 mission. Astronauts including John O. Creighton and Kenneth S. Reightler Jr. deployed the satellite from the shuttle's payload bay using the Remote Manipulator System.

Mission and Scientific Instruments

The primary mission was to measure concentrations and distributions of gases important to ozone chemistry, climate, and atmospheric energy balance. Its ten instruments, developed by teams from the United States, Canada, and the United Kingdom, included the Cryogenic Limb Array Etalon Spectrometer (CLAES) and the Microwave Limb Sounder (MLS). Other key payloads were the Halogen Occultation Experiment (HALOE) and the High Resolution Doppler Imager (HRDI). These tools measured trace gases, temperatures, pressures, and wind velocities from the tropopause upwards.

Operational History and Anomalies

After a successful deployment, the satellite began its planned three-year primary mission, which was later extended due to its continued value. In 2002, a critical attitude control system failure ended its precise science operations, though some instruments continued limited data collection. The spacecraft was officially decommissioned on 14 December 2005. Its final orbit decay led to a highly publicized re-entry over the Pacific Ocean on 24 September 2011, with debris reportedly landing near American Samoa.

Scientific Discoveries and Legacy

The satellite provided the first comprehensive, global data set on the chemistry of the stratosphere, unequivocally linking human-produced chlorofluorocarbons to ozone destruction. Its measurements were vital for validating models used by the Intergovernmental Panel on Climate Change. The mission directly supported the provisions of the Montreal Protocol and its amendments. Its success paved the way for subsequent atmospheric monitoring satellites like the Aura spacecraft and the ongoing Solar Radiation and Climate Experiment mission.

Category:NASA satellites Category:Earth observation satellites Category:Spacecraft launched in 1991