Fractional 143 GHz difference maps on the form (d_{143 - ds1}−d_{143 - ds2}) /d_{143 - ds1}, as evaluated from the real data (top) and from the FFP8 simulation (bottom), both smoothed to 40′ FWHM. The 1% difference observed along the Galactic plane is caused by a mismatch between the measured bandpass profiles (which are used to construct the FFP8 simulations) and those corresponding to in-flight observations. See Sect. 4.3 for further discussion, and Sect. 5.3 for explicit corrections.