Since October, 2018, 1st, some new features concerning clouds detection are implemented in L1 production :
- Consideration of all the parameters’ optimisations evaluated during in orbit test period
- Taking into account a new parameter in the calculations: the minimum height of clouds above the DEM (around 250m)
Nevertheless, an issue on this L1 cloud coverage assessment (cloud mask and cloud_percentage in metadata) exists for the L1 produced and distributed after October, 2018, 1st . Some cloud coverages are wrong, with various situations depending on the real cloud coverage (in extreme cases, some non-cloudy acquisitions have a cloud_percentage value equal to 100%). Thus, the cloud percentage is not reliable since October, 1st.
This does not affect the validity of the products delivered (the products are valid and distributed even for high cloud_percentage values in metadata) . The products which are not valid (and not distributed) are “really” cloudy and not valid.
Currently some complementary tests are carried out (to be the most exhaustive possible in the diversity of the cloud coverage contexts) and this problem should be fixed in the coming days.
NB : The cloud mask for the L2 products is not depending on the L1 cloud mask (except for the Stereo).