Expected KID resonance frequency, ℐ (defined in Eq. (5)), as a function of the sample number within a KISS data bloc. Each data block consists of 1024 samples: the first 128 are dedicated to the modulation, with the remaining samples being dedicated to scientific data acquisition. A⁺ identifies the “interferometric response” in the transmission output (see Sect. 3.3), while the “background response”, B, (see Sect. 3.2) is scaled to 0 Hz; i.e., we subtracted f_tone.