Composite quasar spectra (Vanden Berk et al. 2001), convolved with Gaia’s low-resolution of the Blue and Red Photometers (BP and RP), for the magnitude G = 18 and redshifts z = 0.5, 1.5, 2.5, and 3.5. We plotted the resulting redshifted quasar spectra (black), BP low-resolution (blue), and RP low-resolution (red) spectra for the Gaia wavelength range considering Poisson noise and the photon response curve by Jordi et al. (2010). The blue shaded area indicates the spectral region of the RVS (8470−8710 Å). There are about 37 data bins (Gaia: “samples”) for the blue photometer and 38 samples for the red photometer resulting in example spectra represented by blue and red bars. We applied a typical exposure time for five single field-of-view passages (5 × 4.42 s) in order to calculate the number of photons.