Sentinel 3 OLCI atmospheric correction ICOR

I am processing Sentinel 3 OLCI images and my end goal is to obtain surface reflectance; therefore, I am using ICOR. For the processing parameters, how does one obtain their own aerosol optical thickness value and cloud masking threshold value? Is there a tool I can use in SNAP?

Within ICOR you have the option to either retrieve the AOT from the image or to insert a fixed AOT value. This latter can come from different sources such as from the Aeronet network of sun photometers, CAMS, local measurements, etc.

Multiple default threshold values are used in ICOR for the cloud masking. The default values can manually be modified in the user interface in case cloud masking is not producing satisfying results. I am not aware of tool in SNAP that could be used for it.