Level 1C Data Product

Level-1C product data comprise the unprojected PROBA-V TOA observations that are geometrically and radiometrically corrected.

The two main steps in the Level 1C product processing are:

These processing steps are explained in further detail below.

Geometric processing

Using the Level-1A raw and uncompressed data, a geolocation step is performed for each satellite position to determine the observed pixel’s latitude and longitude. The satellite position and velocity are interpolated for each scan line using an orbital propagation model. The geolocation accuracy is then refined using a geometric Instrument Calibration Parameters (ICP) file. This ICP file contains the variation in detector viewing direction relative to the time out of eclipse and the Sun beta angle. Additionally, the geometric processing model calculates the viewing and solar zenith angles (VZA and SZA, respectively), which are required for further processing steps. The output contains Level-1B data. See Sterckx et al. (2014) for further geometric processing model details. An overview of the geometric performance during the mission is provided at the PROBA-V website.

Radiometric processing

The radiometric processing converts the Digital Number (DN) count in a given spectral band into physical Top-of-Atmosphere (TOA) reflectance values. First, the DN is corrected for detector non-linearities, dark currents, and inter-pixel non-uniformities. Subsequently, these numbers are converted to at-sensor radiance L [W m-2 \(\mu\)m-1 sr-1], using the band-specific calibration coefficients derived from the radiometric ICP file. Finally, the TOA radiance L at a given spectral band is converted into TOA band reflectance.

Information on the radiometric calibration is provided at the PROBA-V website.

Additional details on Level-1C can be found in the PROBA-V Products User Manual.

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