NASA officially announced its intend to develop and launch the Upper Atmospheric Research Satellite – UARS – back in 1979. A group of theorectical investigators were chosen to develop a concept of the spacecraft. 10 Instruments were selected to fly on UARS. The satellite has a Dry Mass of 5668kg (12,500lbs).
Funding delays and the Challenger accident kept the satellite on Earth until 1991 when it launched aboard Space Shuttle Discovery on Mission STS-48. On September 15, 1991, the satellite was released into a 575x580km Orbit with an inclination of 57° using the Robotic Arm of the Shuttle. After deployment, the UARS Spacecraft began a commissioning phase during which its instruments were powered up and checked out. There were no initial problems or instrument failures and UARS was ready for operation. One solar array was used to power UARS, it was rotated to track the sun and to keep providing 1600W of power for the satellite’s intruments. In mid 1992, the array began showing off-nominal signatures.
All instruments were turned off and science observations were halted to investigate the problem. 15 days later, teams re-started the array movements using a work-around procedure. Everything worked normally for about one year when the problem with the drive clutch system occurred again. Technicians resolved to issue by switching to a backup drive and operations continued until 1995 when an Earth sensor failure caused complications that led to stopping the array. A reduced power plan was developed and the instruments operated according to that plan and continued to perform science readings that were sufficient to meet mission objectives. In 1997, another power reduction occurred when one of three spacecraft batteries stopped functioning. Problems didn’t stop and a tape recorder broke in 1999. Only real-time mission data downlink was now possible through NASA’s Tracking and Data Relay Satellite System which captured about two thirds of measurements in any given orbit. Later, instruments ceased taking data due to known factors and consumable expiration. In 2005, 6 of the 10 instruments were still operational when it was decided to decommission the spacecraft. After 14 years and 91 days, the science mission of UARS ended - originally it was planned to last 18-24 months. A final orbital lowering burn was performed before passivation of the satellite commenced. A controlled re-entry was not an option as fuel levels were not high enough to perform a deorbit burn. The orbital lowering burn decreased the on-orbit lifetime of the satellite by about 20 years. In 2006, the International Space Station had to perform a Debris Avoidance Maneuver due to a conjunction with the abandoned UARS Spacecraft. Due to the Orbit-Lowering Burn, the satellite faced an earlier re-entry compared to leaving it in its operational orbit. In September 2011, NASA announced that the satellite would re-enter and burn up to some extent within a month.
For more infor on the Re-Entry and Updates: Visit the UARS Entry Page
CLAES – Cryogenic Limb Array Etalon Spectrometer
ISAMS – Omproved Stratospheric and Mesopheric Sounder
MLS Microwave Limb Sounder
HALOE –Halogen Occulatation Experiment
HRDI – High Resolution Doppler Imager
WINDII – Wind Imaging Interferometer
SUSIM – Solar Ultraviolet Spectral Irradiance Monitor
SOLSTICE – Solar Stellar Irradiance Comparison Experiment
ACRIM2 – Active Cavity Radiometer Irradiance Monitor II
MLS prior to Spacecraft Integration
UARS has contributed to various fields of Earth observation and Research. Its goal was to improve understanding in atmospheric photochemistry and transport. Many studies that UARS contributed to were centered around many open questions about Ozone Depletion. The satellite confirmed a direct correlation between three-dimensional distributions of observed ozone depletion and reactive chlorine. UARS also marked the beginning of uninterrupted long term data records of chemical constituents in the atmosphere. The mission confirmed that human-made chlorofluorocarbons were dominant in the chlorine and fluorine amounts in the stratosphere. The evolution of reactive chlorine over the course of the year was mapped and its role in the springtime polar ozone destruction was confirmed. Additional data was gathered to quantify ozone loss for both, the southern and northern hemisphere. Transport/Movement of chemicals in the amtosphere was tracked over several years and helped scientists understand the dynamics of the hight&mid atmosphere. UARS also provided data on Ultraviolet and visible light that comes from the sun. Those data were essential to gain knowledge on the radiative balance of the stratosphere and mesosphere. UARS provided absolutely calibrated solar ultraviolet spectral irradiances over both maximum and minimum levels for a series of 8 years which set a record at the time. The UARS Mission also helped to develop new methods for identification of atmospheric particle formation and composition via spectral analyses. Also mapped by UARS was the seasonal water cycle in the atmosphere. A variation in water vapor transport from the tropical troposphere to the stratosphere was observed that indicated the link between water transport quantities and changes in temperature in the troposphere. UARS provided data on many more elements of the atmosphere leading to a better understanding of chemical constituents, atmospheric dynamics, particles in the upper atmosphere and external influences on the stratosphere.