Although ozone is found in trace amounts throughout the atmosphere, it is not evenly distributed. Approximately 90 percent of all ozone is contained in the region of the atmosphere known as the stratosphere, which is situated between 15 and 50 km above the Earth's surface. The region below the stratosphere, known as the troposphere, is where our weather phenomena take place. The region of the stratosphere that contains higher concentrations of ozone is generally referred to as the ozone layer (approx. 24 km above the earth's surface).

The ozone layer is thinnest in the tropics and denser towards the poles, though there are large seasonal fluctuations.

Ozone plays a central role in both tropospheric and stratospheric chemistry: it is an important “greenhouse” gas and the ozone layer acts as a natural filter, absorbing most of the sun's biologically harmful ultraviolet (UV) radiation. Depletion of the stratospheric ozone layer would lead to an increase in UV radiation down at the earth's surface, where it could disrupt biological processes and damage a number of materials.

In the 1970’s, scientists realised that chlorofluorocarbons (CFC’s), related halogen compounds, compounds containing bromine and nitrogen oxides (NOx) could all deplete the ozone layer.
CFC's are a common industrial product used in refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of packaging. Nitrogen oxides are a by-product of combustion processes, e.g. aircraft emissions.

However, it was the discovery of a hole in the ozone layer which occurs each spring over Antarctica that focused world attention on the problem and the possible impact that human activities could have on life and human health, leading to unprecedented global action. Through the Vienna Convention on the Protection of the Ozone Layer in 1985, governments committed themselves to protecting the ozone layer and to co-operating with each other in scientific research to better understand atmospheric processes.

The thickness of the ozone layer has been measured for decades at a number of stations using ground-based measurements like spectrophotometers and upper-air in situ measurements with balloon sondes. Those measurements constitute a long-term database of ozone history, but the geographical coverage is incomplete since large regions like Africa and the oceans were left out.

Ozone has been measured using satellites ever since the early 1960s, but only about 15 years ago did the coverage and resolution improve to a point where satellite measurements of atmospheric ozone could become a useful tool in ozone layer studies. A major advantage of satellite measurements is the ability to gather data in remote areas.

Satellite ozone data are mainly used for monitoring the global and vertical distribution of ozone. The vertical distribution of ozone in the atmosphere is an important piece of information for climate study and climate change, while information on total ozone can help to forecast the weather.