Spectral response of LYRA unit 2 channels 3 (left) and 4 (right). The cumulative spectral contribution has been determined by multiplication of the spectral response by the solar spectrum for 1 February 2010 – quiet solar conditions – as deduced from TIMED/SEE and two instruments aboard the spacecraft Solar Radiation and Climate Experiment: the spectral irradiance monitor (SIM) and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) (see text for details).