Wavelength-dependent sensitivity curve of the RGS inferred by TIPS using the NISP and payload module transmission curves characterised at nine positions of the NISP focal plane during the ground-test campaigns (Waczynski et al. 2016; Barbier et al. 2018; Costille et al. 2019; Maciaszek et al. 2022) and spatially averaged in the simulations computing the arithmetic mean of the transmissions measured at the nine positions. Units on the vertical axis are in e s⁻¹ px⁻¹ / (erg s⁻¹ cm⁻² Å⁻¹). This quantity connects the spectra extracted from the slitless data to the physical units presented in this paper.