Why measure solar ultraviolet light?

There are three general areas of scientific interest for which measurements of the solar UV spectrum would help our understanding:

  1. Solar Physics, i.e. the mechanisms responsible for the workings of and changes in the Sun, our nearest star,
  2. the Earth's Upper Atmosphere, i.e. changes resulting from the UV light absorption in the stratosphere, mesosphere, and thermosphere, and
  3. the Earth's Climate, e.g. changes in tropospheric temperatures.
The sun is the primary driving force behind the Earth's climate. Both the sun itself and the climate are changing and evolving consistent with known physical laws. However, due to the very complicated nature of these laws, predictions of their overall effects are uncertain. To understand and properly model the evolution of the state of the upper atmosphere or climate systems, it is necessary to know the spectral distribution of solar light and the energies and fluxes of incoming particles.