Thank you @gmilcinski and @jflasher for your answers. It’s good to hear that more SLC data could become available on AWS!
@gmilcinski, when you say that
SLCs are pretty well compressed, so unzipping everything would cost a lot
do you mean in terms of CPU cost of the unzipping operation, or in terms of storage space?
Actually the SLC tiff files are not compressed, and converting them to COG with compression enabled results in an overall size very close to the size of the original zipped SAFE, while enabling efficient cloud access.
Let’s take an example:
S1A_IW_SLC__1SDV_20191116T205157_20191116T205223_029941_036ABF_1783.zip file size is 4.0 GB. After unzip, the SAFE folder is 6.8 GB. Individual sizes of the 6 tiff files are:
943.2 MiB s1a-iw1-slc-vh-20191116t205159-20191116t205221-029941-036abf-001.tiff
943.2 MiB s1a-iw1-slc-vv-20191116t205159-20191116t205221-029941-036abf-004.tiff
1.2 GiB s1a-iw2-slc-vh-20191116t205157-20191116t205222-029941-036abf-002.tiff
1.2 GiB s1a-iw2-slc-vv-20191116t205157-20191116t205222-029941-036abf-005.tiff
1.2 GiB s1a-iw3-slc-vh-20191116t205158-20191116t205223-029941-036abf-003.tiff
1.2 GiB s1a-iw3-slc-vv-20191116t205158-20191116t205223-029941-036abf-006.tiff
If one re-encodes these 6 tiff files to COG with compression enabled, their file sizes are reduced to
498.0 MiB s1a-iw1-slc-vh-20191116t205159-20191116t205221-029941-036abf-001.tiff
638.2 MiB s1a-iw1-slc-vv-20191116t205159-20191116t205221-029941-036abf-004.tiff
656.9 MiB s1a-iw2-slc-vh-20191116t205157-20191116t205222-029941-036abf-002.tiff
812.7 MiB s1a-iw2-slc-vv-20191116t205157-20191116t205222-029941-036abf-005.tiff
653.0 MiB s1a-iw3-slc-vh-20191116t205158-20191116t205223-029941-036abf-003.tiff
767.6 MiB s1a-iw3-slc-vv-20191116t205158-20191116t205223-029941-036abf-006.tiff
totalling 4.0 GB, which is equivalent to the initial size of the zip.
Efficient cloud access to SLC makes sense because one doesn’t necessarily want to process an entire scene, but rather a single burst in a single subswath (i.e. ~ 1/30 in size with respect to the total scene, for the routine IW mode).