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We outline our techniques to characterise photospheric granulation as anastrophysical noise source. A four component parameterisation of granulation isdeveloped that can be used to reconstruct stellar line asymmetries and radialvelocity shifts due to photospheric convective motions. The four components aremade up of absorption line profiles calculated for granules, magneticintergranular lanes, non-magnetic intergranular lanes, and magnetic brightpoints at disc centre. These components are constructed by averaging Fe I $6302\mathrm{\AA}$ magnetically sensitive absorption line profiles output fromdetailed radiative transport calculations of the solar photosphere. Each of thefour categories adopted are based on magnetic field and continuum intensitylimits determined from examining three-dimensional magnetohydrodynamicsimulations with an average magnetic flux of $200 \mathrm{G}$. Using these fourcomponent line profiles we accurately reconstruct granulation profiles,produced from modelling 12 x 12 Mm$^2$ areas on the solar surface, to within$\sim \pm$ 20 cm s$^{-1}$ on a $\sim$ 100 m s$^{-1}$ granulation signal. Wehave also successfully reconstructed granulation profiles from a $50\mathrm{G}$ simulation using the parameterised line profiles from the $200\mathrm{G}$ average magnetic field simulation. This test demonstratesapplicability of the characterisation to a range of magnetic stellar activitylevels.

Stellar Surface Magneto-Convection as a Source of Astrophysical Noise. I. Multi-component Parameterisation of Absorption Line Profiles