Instruments used for satellite remote sensing of aerosols and clouds were often not designed for this purpose. The longest time series of AOD from Earth Observation (EO) instruments has been obtained from the Advanced Very High Resolution Radiometer (AVHRR), which was designed to measure surface temperature and from Total Ozone Mapping Spectrometer (TOMS), which was designed to measure ozone column concentrations. Time series are discussed in, e.g. Zhang and Reid (2010).