The ground calibration of far ultraviolet scanning imaging spectrometer (FUSIS)

The far ultraviolet scanning imaging spectrometer (FUSIS) is used to measure the composition and distribution of the main molecules and atoms in the Earth's upper atmosphere. It is an important instrument in investigation of the physical and chemical processes in the Earth's upper atmosphere. FUSIS works between 120nm to 180nm, its spectral resolution is better than 1.0nm and its spatial resolution is 8 pixels. This paper describes a kind of ground calibration method and facility of FUSIS. The FUV light is invisible, so all works must be done in high vacuum. The calibration facility includes the FUV light source, collimator, and the vacuum chamber. The pumps of vacuum system can debase the pressure down to 5×10^-5Pa. Calibration experiments are accomplished in the vacuum chamber. The spectral calibration of FUSIS is achieved with the linear interpolation method. The radiation transfer function is deduced. But some factors in the function such as reflection components' reflectivity and detector's quantum efficiency are hard to test accurately. So we use a radiation correction matrix instead of the transfer function in practice. Assuming the FUSIS instrument is a blackbox, the matrix can be tested by experiments. FUSIS can get the absolute radiation intensity of target by calling the matrix.