Images of H-band arc lines for the three segments, illustrating how the data are arranged on the detectors. The dispersion axis is approximately vertical, with longer wavelengths at the top and shorter wavelengths at the bottom. The horizontal axis denotes spatial position. The curved black lines across each detector are the arc lines. Closer inspection shows that these are split into slitlets of 14 pixels, with 14 slitlets making up each IFU, and 8 IFUs across each detector.