Data quality alert: Sentinel-2 Level-2A data conversion issue - 10/27/2026 21:00 UTC #516

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1. talhaabidj commented on Nov 4, 2026

   

   Talha Abid (talhaabidj)

   on Nov 4, 2026

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   Thanks for the alert. We scanned the collection and found 26,116 affected sentinel-2-l2a items. The full list, one item ID per line: sentinel-2-l2a-affected-items.txt

   What we checked

   • We read the write time (blob Last-Modified) of the B03 file of all 74,443 items sensed 25 Oct – 30 Oct 12:00 UTC.
   • We then read pixels from the 35,913 written 27 Oct 17:00 – 30 Oct 06:00 UTC. An affected file's smallest overview never goes above about 300. A healthy one always goes above 1,000, and no file fell in between.
   • For two scenes we compared every pixel of every band with Element84 Earth Search. The PC value equals the true value mod 256 for 100% of pixels. SCL and visual are correct.
   • In a random sample of 80 items, B02, B08 and B11 matched B03.

   What we found (by file write time)

   • Affected: written 28 Oct 01:02 UTC to 29 Oct 21:31 UTC. Every file written in that span that had valid pixels was affected. A further 60 had no valid pixels, so we could not check them.
   • Fine: everything written up to 27 Oct 21:43 UTC, including about 1,450 files written 21:00–21:43, and everything written from 30 Oct 01:04 UTC.
   • The affected items were sensed 27–29 Oct and come from all three satellites.
   • 2,079 affected files were written after this alert was posted.
   • 60 older items we sampled (sensed 2019 – 22 Oct 2026) were not rewritten.

   Not covered: we only sampled items sensed before 25 Oct, and for most items we only checked B03.

   Two of the IDs broke results in our app (water bodies read as land):

   • S2C_MSIL2A_20261029T055941_R091_T42SWA_20261029T093212
   • S2B_MSIL2A_20261028T053929_R005_T43SFR_20261028T092239

   Could you post here when the backfill is done? We'll run the same check again.
2. TaylorCorbett commented on Nov 4, 2026

   

   Taylor Corbett (TaylorCorbett)

   on Nov 4, 2026

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   Thanks for your patience. We completed a backfill from 2026-10-26T12:07:00.000Z through 2026-10-30T00:07:00.000Z. Based on our review all impacted STAC items and assets appear to have been corrected. If you observe any additional impacted items please reopen this issue. Thanks!
3. Taylor Corbett (TaylorCorbett)

   closed this as completedon Nov 4, 2026