Spectral Characterization of Lunar Reflectance: Measurement Campaign for the LIME Model at Izaña Observatory

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An ongoing campaign at the Izaña Observatory (IARC–AEMET) is acquiring direct spectral measurements of lunar irradiance throughout June, spanning from first to last quarter phases of June 2025 to characterize lunar reflectance from the ultraviolet (UV) through the short-wave infrared (SWIR). These high-precision observations will feed into and improve ESA’s Lunar Irradiance Model (LIME). The campaign is a collaboration between the Izaña Atmospheric Observatory and the University of Valladolid (UVa), conducted under the WMO Measurement Lead Center (MLC) (former CIMO-TestBed Program).

This work, carried out by a consortium of scientists from the National Physical Laboratory (NPL, UK), the University of Valladolid (UVa, Spain), the Flemish Institute for Technological Research (VITO, Belgium), and the Spanish Meteorological Agency (AEMET, Spain), constitutes a new extension of the previous LIME2 project. Its goals are to process and model the degree of polarization of lunar reflectance for seamless integration into the LIME Toolbox (TBX); to incorporate a new 2 µm spectral channel; and to refine the interpolation algorithm so the model can deliver continuous, uncertainty-quantified predictions of lunar spectral irradiance from 400 to 2500 nm.

For full project details, objectives, model descriptions, and toolbox documentation, please visit the LIME project website: https://lime.uva.es/.

Figure 1. David Mateos and Javier Gatón at dusk together with the instrumentation used in the campaign (left photo). Another view of the instruments deployed at Izaña Observatory, with the Teide peak in the back (right photo).

Figure 2. Sunrise and moonrise measurements at Izaña Observatory during the field campaign.