Top panel: telescope positions during an elevation scan procedure: 10 steps in elevation have been performed without changing the azimuthal position. Data for absolute calibration are taken in the region between the blue and the red lines. Middle panel: signal in Hz of each valid KID (blue for 1.25 mm detectors, red for 2.14 mm) as a function of air mass, together with the fitted model (black dotted lines). Bottom panel: deduced integrated in-band opacities for the 1.25 mm and 2.14 mm channels.