First Evaluation of PRISMA Level 1 Data for Water Applications

Area of Science:

• Earth Observation
• Radiometry
• Hyperspectral Remote Sensing

Background:

• The PRISMA (PRecursore IperSpettrale della Missione Applicativa) satellite, launched in March 2019, is a new hyperspectral sensor from the Italian Space Agency.
• Accurate Top-Of-Atmosphere (TOA) radiance measurements are crucial for deriving meaningful geophysical parameters from satellite data, especially for aquatic applications.
• Existing sensors like Sentinel-2 play a role in inland and coastal water monitoring, necessitating comparison with new instruments.

Purpose of the Study:

• To perform a first assessment of the TOA radiances measured by the PRISMA hyperspectral sensor in the visible and near-infrared (VNIR) wavelengths.
• To compare PRISMA Level 1 TOA radiances with simulated TOA radiances derived from in situ measurements of water reflectance.
• To evaluate the potential synergy between PRISMA and Sentinel-2 for aquatic applications.

Main Methods:

• Radiometric calibration of PRISMA Level 1 TOA radiances.
• Comparison of PRISMA TOA radiances with TOA radiances simulated using a radiative transfer code based on in situ autonomous radiometer measurements of water reflectance.
• Inclusion of concurrent Sentinel-2 TOA radiance observations in the comparison analysis.

Main Results:

• PRISMA VNIR sensor demonstrated comparable TOA radiance measurements to in situ simulated data, with spectral angle differences (SA) between 0.80 and 3.39.
• Root mean square differences (RMSD) between PRISMA and in situ simulated data ranged from 0.98 to 4.76 [mW m^-2 sr^-1 nm^-1], with slightly higher discrepancies at shorter wavelengths.
• PRISMA TOA radiances showed high similarity to Sentinel-2 data, with RMSD < 3.78 [mW m^-2 sr^-1 nm^-1].

Conclusions:

• The PRISMA sensor is providing reliable TOA radiances suitable for aquatic applications.
• The similarity between PRISMA and Sentinel-2 TOA radiances supports their synergistic use for enhanced water monitoring.
• Further validation with a larger dataset is recommended to fully characterize PRISMA's on-orbit calibration for aquatic ecosystem mapping.