Suspended matter algorithm

Before asking my question, I would like to wish you a Happy New Year 2023. I am personally grateful for the help you are providing us.
My question is what is the algorithm for determining suspended matter. Thank you

A Happy New Year for you too!

There is actually no THE algorithm. But if you are referring to the C2RCC processor there is also no algorithm used in the traditional sense. It uses a neural network to derive the water inherent properties.
You can find the SNAP help several links where the model is described.

And more can be found on the C2RCC community page.
C2RCC – The C2RCC Community web page.