Smith, Natividad; Thomas, Susan; Shankar, Mohan; Priestley, Kory; Loeb, Norman; Walikainen, DaleSmith, N., S. Thomas, M. Shankar, K. Priestley, N. Loeb, D. Walikainen, 2018: Assessment of on-orbit variations of the Clouds and the Earth's Radiant Energy System (CERES) FM5 instrument. Earth Observing Missions and Sensors: Development, Implementation, and Characterization V, 10781, 1078119. doi: 10.1117/12.2324739. The Clouds and the Earth’s Radiant Energy System (CERES) mission is instrumental in monitoring changes in the Earth’s radiant energy and cloud systems. The CERES project is critical in guaranteeing the continuation of highly accurate Earth radiation budget Climate Data Records (CDRs). The CERES Flight Model-5 (FM-5) instrument, integrated onto the Suomi-National Polar-Orbiting Partnership (NPP) spacecraft, joined a suite of four CERES instruments deployed aboard NASA’s Earth Observing System (EOS) satellites Terra and Aqua. Each CERES instrument consists of scanning thermistor bolometer sensors that measure broadband radiances in the shortwave (0.3 to 5μm), total (0.3 to < 200 μm) and water vapor window (8 to 12 μm) regions. In order to ensure the consistency and accuracy of instrument radiances, needed for generating higher-level climate data products, the CERES project implements rigorous and comprehensive radiometric calibration and validation procedures. This paper briefly describes the trends observed in Edition-1 FM5 flux data products that are corrected for inflight gain changes derived from on-board calibration sources. The strategy to detect artifacts and correct for any sensor spectral response changes is discussed. Improvements and validation results of preliminary FM5 Edition-2 products will be compared with Terra and Aqua data products.