ICON Michelson Interferometer for Global High-resolution Thermospheric Imaging Viewing Direction B Temperature

MIGHTI samples the O2 A band spectral region at five different wavelengths in order to both measure the shape of the band and to specify a background radiance that is subtracted from the signal. The wavelengths of the filter passbands are selected to maximize the sensitivity to lower thermospheric temperature variations. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762 nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. Two filter channels sample either end of the band to define a background (754.1 nm and 780.1 nm) and three more sample its shape (760.0 nm, 762.8 nm and 765.2 nm). Using three filters that sample the band shape allows the simultaneous retrieval of the atmospheric temperature and common shifts in the center wavelengths of the pass bands due to thermal drifts of the filters. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere.