A small portable transfer radiometer has been developed as part of an effort to ensure the quality of upwelling radiance at automated test sites used for vicarious calibration in the solar reflective. The test sites, such as the one located at Railroad Valley, are used to predict top-of-atmosphere reflectance relying on ground-based measurements of the atmosphere and surface. The portable transfer radiometer is designed for one-person operation for on-site field calibration the instrumentation used to determine ground-leaving radiance. The current work describes the laboratorybased calibration of the transfer radiometer highlighting the expected accuracy and SI-traceability. Results from recent field deployments of the transfer radiometer are presented to show how the sensor is to be used for 1) evaluating the health of the automated site radiometers, 2) characterizing the surface being measured at the automated test sites, and 3) assessing the error budget for top-of-atmosphere reflectance prediction the test site characterization. Additionally, results from using the transfer radiometer for a radiance-based calibration of the Operational Land Imager are presented.