The FUV instrument takes 2D images of the Earth’s horizon in the Far ultraviolet. The imager is pointing approximately 90 degrees to the spacecraft motion, similar to looking out of the side window of a car as it drives down the road. Onboard electronics read the CCD detectors 8 times per second and collect the data into radiance profiles every 12 seconds. The calibrated level 1 radiances and Level 1 ancillary spacecraft data are combined in a limb retrieval to produce the level 2.4 O/N2 limb product.