Mission Name UARS: Upper Atmosphere Research Satellite SOLSTICE Mission Patch Download LASP SOLSTICE Poster (3347 kb) LASP Instruments SOLSTICE: SOLar STellar Irradiance Comparison Experiment Principal Investigator: Gary Rottman Destination 375 mile Earth Orbit Launch Date September 12th, 1991 Launch Location Kennedy Space Center Launch Vehicle Space Shuttle Discovery Mission Duration 3 years Mission Description/ LASP involvement   LASP Divisions Involved Engineering * Science * Operations LASP Mission Web Page http://lasp.colorado.edu/solstice/ Official Mission Web Page http://umpgal.gsfc.nasa.gov/

UARS helped scientists understand the energy input, chemistry and dynamics of the upper atmosphere and the interaction between the upper and lower atmosphere. UARS studied the processes that lead to ozone depletion, providing three-dimensional maps of ozone and chlorine monoxide near the South Pole.

The primary scientific objective for the SOLSTICE program is to make precise and accurate measurements of the solar ultraviolet (UV) spectral irradiance over the spectral range 119 to 420 nm. SOLSTICE includes three spectrometers to measure over this spectral range and also has the unique capability of monitoring a number of bright stars for deriving the SOLSTICE instrumental degradation rates.

Ultraviolet solar radiation in the spectral interval 120 to 300 nm is almost completely absorbed in the Earth's middle atmosphere. Small changes in the amount of radiation incident at these wavelengths will result in corresponding changes in the photochemistry and energy balance of the stratosphere, mesosphere and lower thermosphere. Recent measurements indicated that solar cycle variability is far smaller than previous estimates. Although the Sun varies by nearly a factor of two at Lyman- (121.6 nm), at wavelengths from 120 to 170 nm the Sun varies by less than 20%. From 180 to 300 nm the variability quickly decreases to less then 1%. The challenge for future observations is to make spectral measurements with a long term accuracy far better then 1%. One approach is to directly compare the solar irradiance to the UV output of a number of bright early-type stars. The SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) is flown on the Upper Atmosphere Research Satellite (UARS) and will make the first comparison of this type.