OMKID spectrometer schematic. The spectrometer targets the 85–110 GHz range with 16 channels. (α) Side view. The radiation is collected through a horn waveguide, a slot termination, a sapphire substrate, and a millimetre-wave transmission line. (b) Top view. The c-shaped filters pick up the signal from the millimetre-wave line. The filtered signal is absorbed by the LEKIDs, which are made of TiAl (with a superconducting gap of 70 GHz). The resonance frequencies of the LEKIDs are monitored with the gigahertz readout line.