What are the observation angles (azimuth and zenith) in OLCI metadata, how do they affect Rrs?

I have some questions about the observation zenith and azimuth angles in the OLCI metadata. Is the azimuth angle (OAA) measured in relation to North or to the sun?

This is more of a theoretical question but I’m wondering if the observation zenith angle would affect the remote sensing reflectance measured by OLCI? Is there some point at which this is “corrected” so that the final Rrs is as if measured from nadir? Or does this not matter (apart from changing atmospheric path length in atmospheric correction?)