Top panels: projected maps of the polarized source (P1) oriented at different angles as seen by the transmission (T) and reflection (R) arrays. Bottom panel: intensity of P1’s maps as a function of the orientation angle for the transmission (T, dashed curves) and reflection (R, solid curves) arrays obtained using an aperture photometry technique and fitted to derive β = 0.8° ± 0.1°. The superposed gray lines represent individual results for the selection of best KIDs.