Getting a satellite on orbit and into operation is one thing. But then you have to collect the data it provides from space and process and provide it as useful information. Ensuring the validity of such data is a lesser-known part of the set-up - but absolutely key to making sure the future work in space is accurate and usable.
This is particularly important with Earth Observation satellites. They are giving us information right now that is being interpolated into international working assumptions about our planet's/climate's behaviour.
This validation is normally done with comparison of known data from ground level measured by airplanes carrying instrument payloads identical to the ones embarked in the satellite actually flying above our heads.
This story explains how ESA is making sure that we receive good data from the Earth Explorer satellite SMOS, which has been surveying soil moisture and ocean salinity since its launch last November.