Jan Dries

The PROBA-V mission: image processing and calibration

With the launch of PROBA-V (Project for On-Board Autonomy – Vegetation) in 2013, the continuity and availability of global land-coverage data in four multispectral bands are ensured for the SPOT (Système Pour l’Observation de la Terre)-VEGETATION user community. This community has been served for already more than 14 years with high-quality 1 kilometre-resolution data. To guarantee continuation of this high quality over the full lifetime of PROBA-V, an operational processing platform and in-flight calibration algorithms have to be in place, which fully consider the specific PROBA-V platform and instrument design characteristics. Data quality has to be ensured for all available product levels, i.e. from the radiometrically corrected radiance data to the 10 day global synthesis. In this article we first focus on some specific design characteristics, which impose some challenges for data processing and calibration. Next, a technical description is given for all the processing steps such as mapping, cloud masking, atmospheric correction, and compositing. The functioning of the Image Quality Centre (IQC) is described. The IQC is in charge of the assessment of the PROBA-V performance, the analysis of the image quality, and the radiometric and geometric calibration after launch. Finally information is given on the distribution of the various products to the user community.

Ten-daily global composites of METOP-AVHRR

Systematic scanning of the earth surface could be achieved for the first time in 1978, with the launch of the earth observation system NOAA-AVHRR. Some twenty years later, the SPOT-VEGETATION instrument introduced significant improvements at the levels of image quality, timeliness and availability. Since the start in April 1998, VITO is responsible for the central processing, archiving and distribution of the VEGETATION data. This paper briefly announces how a similar service is being established at VITO to provide the same kind of image data from the recently launched METOP-AVHRR.

PROBA-V geometric calibration

A system is described for the geometrical calibration of the planned PROBA-V multi spectral earth observation satellite. The largest challenge lies in the complex thermo-elastic distortion due to the absence of active thermal control onboard. The system is based on a 2 step (first by scene, then by global trend), weighted and constrained least squares inversion model. The geometric reference dataset consists in a set of automatically selected image chips from the Geocover 2000 dataset. Results show that the sub-pixel absolute localization accuracy requirements should be reached.