The ESA satellite Gaia aims to measure the main astrometric parameters and generate an astrometric catalogue of 109 objects with an accuracy on the micro-arcsec level. To reach this goal the European scientific community has formed the Gaia Data Processing and Analysis Consortium (DPAC). DPAC includes the Science Operation Centre (SOC) at ESAC and together they constitute the Gaia science ground segment, including a total of more than 400 scientists and engineers. Such a large group of developers represent a massive development effort which requires effective quality monitoring and assurance mechanisms and reporting structures to be in place. In this paper we will outline the procedures and mechanisms setup within the consortium to assure that DPAC software products and the necessary hardware will be ready when they are needed and fulfill their expectations. The experiences gathered in the employed PA/QA process, which is based on the relevant ECSS standards, will be described and will prove useful for other projects of similarly large scale.