As part of the Phase C of the LSST:UK Science Centre (LUSC) programme, a new contribution will focus on providing infrastructure for the accurate estimation of the clustering of galaxies, which is of central importance to the cosmological science to be carried out by the Dark Energy Science Collaboration, as well as galaxy evolution studies targeted by the Galaxies Science Collaboration. The work will be carried out between the University of Oxford and Imperial College (PIs: Alonso & Leistedt) and will aim to model the non-cosmological modulation of galaxy density caused by Galactic and observational sky contaminants (e.g., dust extinction, stars, PSF fluctuations). This will involve a combination of well-established techniques (e.g. foreground templates fitting and deprojection) as well as new ones based on Source Injections (SI), where mock objects are added to images which are reprocessed in order to characterise system responses and sensitivity to foregrounds. SI are promising but require the development of new algorithms and new infrastructure to be embedded in the DESC and GSC software ecosystems. This contribution will tackle this challenge and validate the associated software on early Rubin data to model the survey’s transfer function in detail.