Lunar observations make it possible to compare radiometric performance of multiple remote sensing satellite instruments on orbit. In this paper, the lunar calibration inter-comparison methodology developed for MODIS and VIIRS and GSICS (Global Space-based Inter-Calibration System) Implementation of the ROLO (GIRO) model for on-orbit radiometric instruments are extended to include the Global Change Observation Mission - Climate (GCOM-C) Second generation Global Imager (SGLI) observations. Preliminary results of the inter-comparison of SGLI-Visible and Near-infrared Radiometer (SGLI-VNR), Aqua MODIS, and SNPP VIIRS over a wide range of wavelengths are 3.7-7.7% for bias and 3.8% for uncertainty. The SGLI radiometric responses relative to the GIRO model are in family with those observed by the heritage instruments.