Interference from the drive electronics of the 4 K cooler in the HFI detectors. Left: measured 4 K line amplitudes for the most intense lines in bolometer 143-3a. Right: new 16.03 Hz line template amplitudes for bolometer 100-1b. For unknown reasons, the line is only detected intermittently around day 300. For reference, the CMB temperature fluctuations typically fit within ±250 μK and polarization fluctuations within ±2 μK; it is therefore clear that the cooler lines must be modelled and removed to high precision. With the Planck scan rate being 6° s⁻¹, the 10 Hz line corresponds to an angular scale of 36′ and multipole ℓ ≈ 600. For higher-order harmonics of 10 Hz, divide the angular scale and multiply the multipole with the appropriate factor.