Pandora is a relatively new UV-VIS instrument for measuring total ozone and also ozone profiles in a similar way as MAX-DOAS instruments. The instrument is relatively small, inexpensive and automatic. The number of Pandora instruments has been growing during recent years and therefore it is possible that a network of Pandoras could have stronger role in satellite validation in the future. For example, the European Space Agency has recently supported the development of Pandora network called Pandonia.

However, so far only a few studies exist which describe measurement uncertainties or measurement validation (see e.g. Herman et al. 2015, Tzortziou et al, 2012). This yields low confidence that the measurement uncertainties are currently either fully documented or rigorously quantified. For example, systematic uncertainty in Pandora direct-sun measurements are limited by temperature effects not corrected in current operational procedures. The neglect of temperature effects (related to the ozone spectroscopy in the Huggins bands) leads to seasonally dependent systematic biases and synoptic scale biases, of various amplitudes depending on the latitude of the site. This gap is partially addressed within GAIA-CLIM.