ADC correction

The ADC nonlinearity correction affects the modulated signal of the bolometers, before 40 of these fast samples are averaged and transmitted to the ground. The TOI data delivered in the HFI products are made up of these averaged values, with the raw signal of a bolometer for one modulation period being transmitted only at sparse intervals. This averaging necessitates a complicated process to remove the systematic effects associated with the ADC nonlinearity on the modulated signal, taking into account the 40-Hz parasitics associated with the 4-K cooler drive electronics.

The principles of the correction are detailed in Planck-2015-A07. The correction cannot be done using only the TOI values, but requires ancillary data from ground-based tests and additional tests done during the LFI extension of the mission, when the dilution cooler no longer operated. For this reason, we do not describe here any details that are not already in the paper, since the users should not expect to be able to improve this part of the processing.