Sardinia Salty Pond area for CAL/VAL activities for supporting hyperspectral orbiting mission

A comparative analysis was conducted between the data acquired by ASI-PRISMA (Agenzia Spaziale Italiana-PRecursore IperSpet-trale della Missione Applicativa) and DLR-EnMAP (German Aerospace Center - Environmental Mapping and Analysis Program), along with field spectrometer measurements. The chosen test site, situated at the 'Sale’e Porcus' pond in Western Sardinia, Italy, exhibits notable homogeneity, rendering it an ideal location for calibration purposes. The two agencies, ASI and DLR, acquired three remote sensing data acquisitions from July 14th(DLR-EnMAP), 15th (ASI-PRISMA) and 22nd (DLR-EnMAP) 2023. On the data acquired on July 22nd, DLR-EnMAP showed an overestimation of radiance in the VNIR region compared to both ASI-PRISMA (15th July) and the DLR-EnMAP data (14th July). However, all datasets closely align up to 2500 nm across all the considered days. Despite a slight time acquisition difference of 8 days, the relative mean difference between reflectance values estimated by ASI-PRISMA and DLR-EnMAP on the test area is approximately 5%. The maximum relative difference occurs at the spectral range's beginning and end, reaching around 10%. The study delves into the relationship between the averaged ground truth reflectance values characterizing the test site and the reflectance values derived from official catalogues. FieldSpec measurements validate the quality of reflectance estimations for both ASI-PRISMA and DLR-EnMAP.