The GOES-16 satellite was launched on 19 Nov 2016, and it became operational as the GOES-East satellite on 18 Dec 2017. The GOES-17 satellite was launched on 1 Mar 2018, and it became the GOES-West operational satellite on 12 Feb 2019. The Advanced Baseline Imager (ABI) is one of six instruments onboard GOES-16 and GOES-17. It has 16 multispectral bands in the 0.45 µm to 13.56 µm wavelength range. This study is focused on bands 1–3, 5, and 6, which reside in the solar-reflective region (0.4 µm to 2.5 µm). The five bands used in this work have spatial resolutions of 500 m (band 2), 1000 m (1, 3, and 5), and 2000 m (band 6). The geosynchronous orbit of GOES provides a unique opportunity for the Radiometric Calibration Test Site (RadCaTS), which is an automated facility at Railroad Valley, Nevada, USA. RadCaTS consists of ground-based instruments that measure the surface reflectance and atmosphere throughout the day. It was developed by the Remote Sensing Group of the Wyant College of Optical Sciences at the University of Arizona (UArizona), and it is currently used to monitor such low-Earth orbit (LEO) sensors as Landsat 7 ETM+, Landsat 8 OLI, Terra and Aqua MODIS, Sentinel-2A and -2B MSI, SNPP and NOAA-20 VIIRS, and others. The improved spectral, spatial, and temporal characteristics of ABI create an excellent opportunity to intercompare results obtained from a geosynchronous sensor to those obtained from typical LEO sensors.