The SSI spectrum comparison of TSIS-1 SIM (red) and SORCE SIM (black) for the overlap time of TSIS-1 and SORCE missions covering the full range of 200–2400 nm (note: wavelength is plotted on a log-scale). Both spectra are plotted on their native irradiance scales (no scaling applied). The inset shows the ratio (green) as a function of wavelength over the 240–2400 nm range (below 240 nm, the SORCE SIM has large relative uncertainties). Clearly seen is the lower IR SSI longward of 900 nm, up to ~6% lower for TSIS-1 SIM. However, excellent agreement is seen throughout the visible where the SSI is a maximum.