During the remainder of the mission, the nominal scanning law has been used. See Section 1.3.2 and Gaia Collaboration et al. (2016) for details. During the nominal five-year mission, the nominal scanning law results in an average of ∼70 usable transits for a given star. It should be noted that, as a result of the scanning law, there is a significant variation of the number of end-of-mission transits as function of position on the sky, in particular as function of ecliptic latitude β with regions around β≈45 ∘ being observed more often and regions around the ecliptic poles and plane being observed less frequently. The number 70 assumes that ∼20% of the transits collected on board do not produce useful information, for instance as a result of on-board data deletion (Section 1.1.3 and Section 1.3.3). In practice, this is a conservative estimate, in particular for bright stars (Table 1.10).