Descomposición H-a Alfa en SNAP

por favor ise el siguiente procesamiento (subset-calibracion-correcion de terreno-enmascaramiento con schape ) y me arroja este error por favor una sugerencia sobre la correcta procesamiento

Your product needs to be a dual pol SLC to use the dual pol decompositions and a quad pol SLC to use any of the other decompositions.
It looks like your product has already been terrain corrected and speckle filtered.

With an SLC product, you could apply calibration with complex output, polarimetric speckle filter then polarimetric decomposition. As a last step you can then terrain correct.

muchísimas gracias en que pagina descargo los producto SLC