A log plot of the average transmit power ﹩{P}_{A}^{T}﹩ in mW against the coverage solid angle Ω_A, with all other parameters taken from Tables 1–4. Two wavelengths are plotted, and for small Ω_A the required transmit power is much larger at the longer wavelength owing to the greater relative aperture sensitivity to interference and additionally the larger irradiance of a red dwarf star.