The following processor upgrades were implemented since the beginning of the mission for generating PROBA-V Synthesis products (Level 3):

• Oct 2013 (First Processor - Collection 0): The first operational PROBA-V data were disseminated at 16 October 2013 as V1. 
• 27 Nov 2013 (Radiometric Correction): During the first few weeks, it was found that a radiometric correction was necessary. All operational data were then reprocessed and data from 16 October – 26 November 2013 was renamed to V2. 
• 13 June 2014 (Compositing Rule upgrade): Changes in the synthesis compositing rules were implemented for both the 300 m and 1 km products in order to be consistent with the SPOT-VGT processing chain, reprocessing was finalised by September 2014. Product files from 27 November 2013 onwards were renamed from V1 to V2, while product files from 16 October – 26 November 2013 were renamed from V2 to V3. The changes implemented for this upgrades include in particular:
  • The VZA angle rule was switched off for the 1 km compositing. This was decided for consistency reasons with respect to the SPOT-VGT 1 km products.
  • The 'Bad SWIR' rule was switched off for the 1 km compositing: initially, a 'good' radiometric quality for all bands was required. However, for consistency reasons with respect to SPOT-VGT, especially for the NDVI product, it was decided to exclude the SWIR channel from these requirements.
  • The time grid resolution was changed from days into minutes for the 100 m, 300 m and 1 km compositing. This change enables users to perform a proper atmospheric correction. 

• 30 June 2016 (Second Processor - Collection 1): A second processor has been developed for the improvement of the quality of the PROBA-V products.

  The current processor software version, used for a full reprocessing of the PROBA-V archive and also for the operational ground segment includes significant quality improvements:

  • re-fined radiometric calibration parameters

  • metadata compliancy to Climate and Forecasting convention (v1.6)

  • new Cloud Detection Algorithm

  • the intermediate L2a products are made available with this reprocessing
     

The main improvement of the new PROBA-V processor compared to the previous version is the cloud detection algorithm. The PROBA-V cloud detection algorithm employs multiple thresholds-based approach to identify clouds.

The primary input to the PROBA-V cloud mask is based on the usage of climatological maps of albedo (monthly averages obtained from the GlobAlbedo dataset). In addition to the GlobAlbedo dataset, also a 10 years global climatology of monthly means of MERIS reflectances in the blue band was used. This auxiliary information is used to design a "dynamic threshold" algorithm, with cloud tests customised for each status class (land, water, snow/ice, unknown land cover).

The new dataset, defined as Collection 1, is identified by the new version number "V101", replacing the old "V001" used previously. More detailed information on all changes implemented for the reprocessing campaign is available in the User Manual. 

Note that the detailed information on the used versions of the various algorithms (Geo-modelling, Radio-modelling, Mapping, Mosaicking, Clouds/Snow detection, Shadows detection, Atmospheric Correction, Compositing) can be found in the product file meta data attributes (Level 3 Group).