The OMPS sensors are required to have 15% or less degradation in optical throughput due to contamination and particle obscuration in each channel of the instruments at the end of life. Orbital optical throughput degradation of OMPS nadir system, NM (300 to 380 nm), and NP (250 to 310 nm) has been observed and variations in degradation of are evident. The percent degradation of optical throughput was analyzed through a track of the change in sensors’ optical throughputs. Specifically, the sensors’ optical system is tracked with the reference solar diffuser, and degradation of the working solar diffuser is tracked by comparison of the working and the reference solar diffusers. For this study, the instrument that is the most sensitive to contaminants establishes the allowable contaminant levels of the entire suite after the first three-year operation. Figure 11 shows the optical throughput changes for six selected wavelengths, three on the NP and three on the NM, that well represent behaviors of all other wavelength channels. The data used in the analysis was collected from the measurements of the reference (green) and the working (red) diffusers and was fully calibrated. Results are presented for the lowest operating wavelength of each instrument, where contamination sensitivity is the highest. The NP is the most sensitive to contamination and has the most optics and the lowest operating wavelength; analysis indicates that the NP sensor has a higher degradation and, therefore, higher contamination levels. For the operating wavelengths of OMPS, the lowest wavelength corresponds to the highest absorption coefficients and, therefore, the highest throughput losses for the molecular contaminants. This, in turn, raises the degradation due to this type of contaminant. In addition, the NP has 13 optical surfaces, as opposed to 11 in the NM. Annually recurring features in both the NM and NP solar data have been observed from Fig. 11, which is associated with a variation of the solar beta angle. Comparable results are observed for other wavelengths. The feature is correlated with solar beta angle variation from diffuser measurements.