Tropospheric ozone has an impact on air quality and acts as a greenhouse gas and therefore plays a role in public and environmental health, as well as climate change, linking the two subjects. Establishing processes and trends in tropospheric ozone, in particular in the free troposphere, above the mixed layer and below the stratosphere, is difficult due to a lack of direct observational data. Tropospheric ozone is much more variable in space and time than stratospheric ozone due to transport and chemistry. The frequency and accuracy of the observations should ideally be adjusted to account for this elevated variability. In addition, the balloon borne ozone samplers are optimised for stratospheric observations, which implies sub optimal performance in the troposphere. Therefore, other observational techniques are required to fill the need for observations of tropospheric ozone from non-satellite sources that are more routinely operational. Contrary to stratospheric ozone, passive satellite observations have limited access to information about tropospheric ozone as the TOA down view is largely dominated by the much higher stratospheric loadings across the sensitive regions of the E-M spectrum. However, currently planned missions are envisaged to have better tropospheric ozone sensing capabilities. Also, ozone soundings using balloon borne samplers are too scarce to capture the relatively high spatial and temporal variability in the troposphere.