Multiband Ionospheric Ultra-Violet Spectrum Imager (MUSI) onboard the Fengyun Satellite

The dynamic thermosphere-ionosphere (T-I) system exhibits a significant response to energy inputs from magnetosphere and lower atmosphere, which leads to rapid changes and regional disturbance in the ionosphere. To monitor the T-I system over China in real time, a Multiband Ionospheric Ultra-Violet Spectrum Imager (MUSI), with a launch scheduled for 2025, will be hosted on the Fengyun-4C satellite, which is in geostationary orbit at 133°E longitude and supported by the China Meteorological Administration. MUSI is an imaging spectrometer. It will provide an opportunity to understand spatial and temporal variability of the T-I system over China due to different kinds of energy inputs by measuring the Earth’s far ultraviolet (120-160 nm) airglow with spectral resolution of 0.4 nm. MUSI’s field of regard is 14° East-West and 16° North-South. The observations includes simultaneous monochromatic images of the sunlit and nightside disk each day produced at four ‘colors’, i.e., HI 121.6 nm, OI 130.4 nm, OI 135.6 nm, and 140-160 nm N₂ Lyman-Birge Hopfield bands. Further information, such as the O/N2 column density ratios during the day and the ionospheric peak electron density during the night, will also be derived.