Enable Sentinel-1 EW SLC Processing

[abradley60]

Enable Sentinel-1 EW SLC Processing

Adds support for processing Sentinel-1 Extra Wide (EW) mode SLC data through the OPERA RTC pipeline. Like IW mode, EW SLCs contain burst-level information that can be processed using the RTC tool. Below is a sample EW NRB burst product from the file S1A_EW_SLC__1SDH_20220330T185405_20220330T185511_042554_051380_3E95

Burst ID : t132_256983_ew4

Overview of Changes to RTC Code

A small amount of additional logic is required in the RTC project to detect whether an input Sentinel-1 SLC was acquired in IW or EW mode, and to set the number of sub-swaths accordingly before passing to s1-reader (3 for IW, 5 for EW).

NOTE These changes add new functionality without altering existing IW processing capabilities, and the RTC changes can therefore be merged independently of the dependent projects.

Other Dependencies to enable EW SLC processing

Full EW processing requires the following to be in place:

• s1-reader updated with the changes proposed in Enable Sentinel-1 Extra Wide (EW) SLC compatibility  isce-framework/s1-reader#153
• If a burst_database_file is required, it must be generated using burst_db with the changes implemented in the following PR Enable opera-db create for Sentinel-1 EW mode burst_db#140. A flag can now be specified to generate the equivalent database for EW mode, e.g. opera-db create --sensor-mode EW.

The dependencies for RTC will therefore need to be updated with these changes to enable EW processing.