Description
Small Python tool (`asfsmd`) that allows one to download XML files containing Sentinel-1 products metadata from the ASF archive.
Sentinel-1 products are stored in the ASF arcive as ZIP files that are quite large because they contain both the products annotations and the binary image data.
The `asfsmd` tool is able to retrieve only the relatively samll annotation files (in XML format) without downloading the entire ZIP archive.
`asfsmd` exploits Python packages like `fsspec` or `httpio` for reading HTTP resources as random-access file-like objects. In order to do it the remote server must support the `Range` header.
This approach allows one to open the ZIP archive remotely, inspects contents, and download only the pieces of data that are actually necessary to the user.
Performnces of this approach are quite poor but, in the specific case of Sentinel-1 products, the entire process results to be faster than downloading the entire ZIP archive and extracting only annotation files.