Common Reference Channels for Metrological Comparability

In this article we discuss the effect of the choice of reference during calibration on later use of the calibrated results, and how a reference should be chosen to support later use of the data. Starting from the concept of metrological comparability we will formulate the purpose of calibration in metrology, and discuss the difference from a traditional (statistical) view. We derive some requirements for calibration, and especially for the choice of a useful reference. The calibration of a geosynchronous (GEO) instrument with a low spectral resolution against a low-earth-orbiting (LEO) instrument with a much higher spectral resolution used as a reference, as is currently done in GSICS, raises the question how the processing of the data from the reference sensor is affecting the aim of calibration.