The Remote Sensing Group (RSG) at the University of Arizona Optical Sciences Center has been performing high accuracy laboratory calibration for over 20 years. An integral part of this laboratory calibration is the implementation of very accurate and repeatable transfer radiometers. This work highlights the design and characterization of one such radiometer. This particular radiometer is essentially an updated version of a previous radiometer designed and characterized by the RSG (Spyak 2000) with particular attention being paid to increased portability, ease of use and autonomous operation. This work also covers the characterization of this radiometer, including radiometric calibration, field of view, and general performance.