Heat rejection requirements for the Photovoltaic Radiator (PVR) are derived from the Photovoltaic Module power generation and storage system electrical power requirements imposed by NASA. The requirement has been added to provide heat rejection for the Early Extended Active Thermal Control System (EEATCS) to support the Assured Early Research phase of the International Space Station (ISS) Mission. Early mission requirements have resulted in two of the units being coated with a silver Teflon tape. The original Thermal Control System (TCS) requirements require one of the units to be coated with Z-93.Qualification testing of the PVR includes both single panel and assembly level testing. Single panel testing is part of a qualification test program, which is designed to verify the pressure drop and thermal performance of the PVR. Testing of the panels requires the integration of compatible test systems including instrumentation and data acquisition, an environmental control system and an ammonia flow system.Thermal vacuum performance tests of two PVR panels, silver Teflon and Z-93, have been conducted. This paper describes the test hardware and operation, and the methods employed to obtain viable test data. Emphasis is placed on simulating on-orbit environments and comparison of test results to thermal and hydraulic math models.