Illustration of the disk R50 effect on the quality of the spectra. Top two panels: 2D extracted spectra obtained from one dither of the EWS simulation for two sources with disk R50 = 0.″5 and disk R50 = 1.″5 centred on the Hα-complex line which is highlighted with a black circle. Bottom two panels: the corresponding ID extracted spectra, resulting from the SIR data processing pipeline on four dithered frames. The signal and RMS spectra are shown and centred on the Hα-complex line measured with S/N of 9.1 for the 0.″5 source (red line) and 4.5 for the 1.″5 source (blue line). Values of the flux and RMS on the vertical axis are expressed in erg s⁻¹ cm⁻² Å⁻¹.