Difference Between Mueller and Kennaugh Matrix

What is the difference between Mueller and Kennaugh matrix? I notice some text considers them the same while the others not. As far as I have read so far, Kennaugh matrix is considered symmetric while Mueller matrix not. I think they both connect the input Stokes vector to the output Stokes vector.

Maybe this extract helps you


Source: Polarimetric Radar Imaging: From Basics to Applications - Jong-Sen Lee, Eric Pottier - Google Books

@ABraun I don’t really understand the concept of forward and backward scattering. Since we are dealing with backscattered signals from the satellite (monostatic systems) is backward scattering not the only way?