Change of Sentinel-2 scenes


I noticed that a pair of scene downloaded some months ago are changed now (the old scenes have been replaced by new data of the same acquisition). Probably they have been reprocessed because the creation date in the product name is different (products generated before the 6th of December, 2016). Here some examples:

  1. it is: S2A_OPER_PRD_MSIL1C_PDMC_20160720T235233_R079_V20150807T095007_20150807T095007.SAFE
    it was: S2A_OPER_PRD_MSIL1C_PDMC_20160319T131649_R079_V20150807T095007_20150807T095007.SAFE

  2. it is: S2A_OPER_PRD_MSIL1C_PDMC_20160706T143104_R022_V20150823T101019_20150823T101019.SAFE
    it was: S2A_OPER_PRD_MSIL1C_PDMC_20160315T111433_R022_V20150823T101019_20150823T101019.SAFE

Please, can you help me to understand this changes? what is changed exactly in the processing (if it is changed)? May I use the processing baseline number to understand the change or is there something else in addition to that?
Moreover, according your knowledge was there a change for the cloud mask algorithm detection or not?

In the Data Quality Report (09/01/2017) I read (pag.17/31).:

"A reprocessing campaign of images acquired during the commissioning period (from launch till 30/11/2015) has been completed.
A few products with a major anomaly have been released during the reprocessing campaign:

  • All products with sensing time before 30/11/2015 and baseline number 02.01 and 02.02 (geolocation and mis-registration errors)
  • Product from September 2015 processed between the 13 and the 26 of October 2016 (incorrect quantization level)
  • Products from 24 and 25th of September 2015 processed on the 29th of December 2016 (incorrect quantization level)
  • Products from orbits 1296 to 1304 processed on October 2016 (large geolocation error due to a GPS anomaly)
    These products are progressively removed from the archive and should not be used"

Is here the answer I’m looking for?

Thanks in advance.

Dear Ross,

i noticed that some images have erros if we say about geolocations (images released earlier eg. in march could have errors and latest versions have corrected geolocalizations). I also noticed that “newer” images have a littlte differents in reflectance (different is 0,01 % beetwen channels). Thats all. Dont worry. I downloaded some images that released third time eg two times in march 2016, October 2016 (for single granules) and endless in January 2017 for all scene ( try for date for Poland 2015-08-20).

Best Regards

Check the processor version in the metadata. If it has changed to a higher number (e.g. from 02.01 to 02.04) it means that it is re-processed. 02.04 is supposed to repair a number of geolocation problems found earlier, so should be better for multi-temporal stacking.