AKA: Upper Atmosphere Research Satellite. Status: Operational 1991. First Launch: 1991-09-12. Last Launch: 1991-09-12. Number: 1 . Gross mass: 6,795 kg (14,980 lb). Height: 9.80 m (32.10 ft).

The vehicle provided measurements of atmospheric internal structure (trace constituents, physical dynamics, radiative emission, thermal structure, density) and measurements of the external influences acting upon the upper atmosphere (solar radiation, tropospheric conditions, electric fields). The specific UARS mission objectives were to study energy input and loss in the upper atmosphere, global photochemistry of the upper atmosphere, dynamics of the upper atmosphere, coupling among these processes, and coupling between the upper and lower atmosphere. The spacecraft was 3-axis stabilized via reaction wheels, torque rods to 36 arc seconds. Attitude knowledge to 20 arc seconds used star trackers, Earth sensors, an inertial reference unit, and Sun sensors. The single solar array was 1.5 x 3.3 meters and generated 1.6 kW, recharging 3 x 50 A-hr batteries. The hydrazine propulsion system provided for orbit insertion and maintenance. S-band communications was via low gain antennas and a gimbaled high gain antenna through TDRSS. The payload included:

• Cryogenic Limb Array Etalon Spectrometer (CLEAS).
• Improved Stratospheric and Mesospheric Sounder (ISAMS).
• Microwave Limb Sounder (MLS).
• Halogen Occultation Experiment (HALOE).
• High Resolution Doppler Imager (HRDI).
• Wind Imaging Interferometer (WINDII).
• Solar-Stellar Irradiance Comparison Experiment (SOLSTICE).
• Solar Ultraviolet Spectral Irradiance Monitor (SUSIM).
• Particle Environment Monitor (PEM).
• Active Cavity Radiometer Irradiance Monitor (ACRIM II).

• UARS - . Payload: Discovery F13 / UARS. Mass: 6,795 kg (14,980 lb). Nation: USA. Agency: NASA Greenbelt. Class: Earth. Type: Ionosphere satellite. Spacecraft Bus: MMS. Spacecraft: UARS. Decay Date: 2011-09-24 . USAF Sat Cat: 21701 . COSPAR: 1991-063B. Apogee: 582 km (361 mi). Perigee: 574 km (356 mi). Inclination: 57.00 deg. Period: 96.20 min.

  Upper Atmospheric Research Satellite; deployed from STS-48 on 15 Sepetember 1991. It studied the depletion of the ozone layer, confirming that CFCs cause the `ozone hole', and improved models of upper atmosphere chemistry, including studies of methane in the Antarctic, sulphur dioxide from volcanoes, and global wind measurements. Some media hysteria surrounded its reentry on 24 September 2011, but it apparently came down unobserved in the Pacific Ocean east of Hawaii.