Far ultraviolet nighttime ionospheric photometer

<p>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\&nbsp;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\&nbsp;counts/s/Rayleigh at 135.6\&nbsp;nm with stray light less than\&nbsp;2\&nbsp;\%. Some tests of the instrument have been conducted and the results will be discussed in the end.</p>