Profiles of Euclid’s diffraction spikes. Diffraction spikes of the star HD 1973 analysed through photometric extraction profiles (at the bottom) juxtaposed with the star’s halo profile in a corresponding lighter shade (as illustrated in Fig. 26). This comparison highlights the pronounced dominance of spike brightness over the halo, becoming evident beyond a radius of a few arcseconds. Additionally, a simulation of the four spikes extending to a 400ʺ radius (with matching colours, and the H_E-band arbitrarily set to μ₀ = 10 for the purposes of this plot) corroborates the relative surface brightness of the spikes as observed across the four Euclid bands. Unlike the halo that adheres more closely to a 1/r³ function consistent with the Bessel envelope at high radius, the spike profiles, as anticipated, approximate a 1/r² function.