ESA Project 1: Lunar spectral irradiance measurement and modelling for absolute calibration of EO optical sensors (2017-2019)

This project, launched in 2017, was assigned to a consortium of three members: University of Valladolid/IzaƱa Atmospheric Reseach Center, National Physical Laboratory (NPL, London) and Flemish Institute for Technological Research (Vlaamse Instelling voor Technologisch Onderzoek, Belgium). The main goal of the project is to use ground-based lunar measurements performed with a CE318-TP9 photometer to improve the modelling of the lunar disk irradiance variations through its cycles with a threshold of 2% in the final model uncertainty.

Figure 1.- LIME lunar irradiance model at 440 nm for the lunar phase angle range between -100 and 100 degrees.

The main outcome of this project is the new lunar irradiance model LIME (Lunar Irradiance Model ESA). LIME is an improved lunar irradiance model with < 2% absolute radiometric uncertainty (SI traceable), derived from 150 nights of lunar observations at IZO and TPO stations and an uncertainty analysis based on a Monte Carlo Evaluation (Figure 1). These results improve considerably the absolute radiometric uncertainty involved in the previous lunar models (~ 5-10 %). This new model is expected to play an important role in EO radiometric calibration, which can be validated using radiometrically stable natural targets, like the lunar disk irradiance. With this information, EO measurements can be radiometrically linked to all past, present and future sensors having performed similar measurements.

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