Far ultraviolet nighttime ionospheric photometer

Far Ultraviolet Nighttime Ionopsheric Photometer (FNIP) is a newly-designed instrument for low earth orbit missions, observing the earth night airglow nadir at OI 135.6\ nm emission produced by ionospheric O++e recombination and receiving the horizontal information on nighttime ionosphere with a spatial resolution of about 1.6o\texttimes3.8o. This simple, highly robust instrument excludes OI 130.4 nm emission and Herzberg oxygen bands with lower power and approximately achieves a sensitivity of about 400\ counts/s/Rayleigh at 135.6\ nm with stray light less than\ 2\ \%. Some tests of the instrument have been conducted and the results will be discussed in the end.