Compact polarimetry is something that differs from Sentinel 1 in the sense of transmitting and receiving wave combinations. Compact polarimetry is three beautiful combinations of dual polarimetry. The classes are as follows.
Pi/4 Compact polarimetry:- Tx: Pi/4 linear, RX: H linear & V linear
Dual Circular Pol (DCP) Compact-polarimetry:- Tx: Circular, Rx: Circular
Hybrid-polarimetry: Tx: Circular transmit, Rx: H linear, and V linear.
Obviously, Sentinel-1 has different transmitting-receiving combinations, so the compact polarimetry algorithms can not be directly implemented for the processing of Sentinel-1 data, however, you can modify compact-pol methods to make them suitable for Sentinel-1 data.
I just saw a literature that SAR sensors like RADARSAT, DESDynI and RISAT are circular polarisation and Sentinel-1 is linear polarisation. I have a doubt that whether is it possible to compute Compact pol-radar vegetation index with Sentinel-1?
May I know what kind of modification need to done while in preprocessing steps?