The XUV Photometers (XPs) are silicon XUV photodiodes with thin film filters to measure the integrated solar UV irradiance from 0.1 to 35 nm with a typical bandpass of 7 nm. These silicon XUV photodiodes are reference detectors for NIST in the XUV spectral region because they are extremely stable. The XPs are not expected to degrade by more than a couple of percent over the SORCE mission based on the stability tests that NIST and others have performed on these photodiodes as a function of exposure level to photons and high energy particles. Because the solar variability below 35 nm is expected to be a factor of 2 to 1000 (wavelength-dependent), the XPs can serve as an on-board reference detector. The estimated uncertainty for this assumption of detector stability is about 2%, as proven for the SNOE XPS and TIMED SEE XPS.