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The Heat Rejection Subsystem (HRS) Radiators Orbital Replaceable Unit (ORU) for the International Space Station has undergone thermal vacuum qualification testing at NASA Plum Brook Station, Space Power Facility in Ohio. The testing was conducted from December 1996 through January 1997 and October 4 through 18, 1997. This testing included confirmation of the heater control assembly (HCA) and heater performance that was initially tested during December 1996 through January 1997. Deployment system functional operations were tested for both hot and cold conditions using both the Integrated Motor Control Assembly (IMCA) and the Extravehicular Activity (EVA) drive.

The Photovoltaic Radiator (PVR) is designed to reject waste heat of the Early External Active Thermal Control System (EEATCS) and the Photovoltaic Thermal Control System (PV TCS) of the International Space Station (ISS). Two EEATCS PVR units and one PV TCS PVR unit will be on the Assured Early Research (AER) phase of the ISS and all four PV TCS PVR units will be on the assembly complete configuration of the ISS. Thermal environments of the AER mission and assembly complete configuration present challenging thermal designs to maintain the EEATCS and PV TCS PVR units functioning within the temperature operating limits of the structural components and the ammonia fluid.

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.