This paper presents the COMmercial Experiment Transporter (COMET) Service Module thermal control system design using a Capillary Pumped Loop (CPL). The COMET satellite is scheduled for launch in early 1993 aboard the Conestoga rocket. COMET provides the United States commercial research and development community with a dependable and economical means to access space. The COMET program is defined and funded by the NASA Centers for the Commercial Development of Space (CCDS). The Center for Space Transportation and Applied Research (CSTAR) was given the authority to establish and implement the COMET Program.COMET is designed to carry experiments to the micro-gravity of space and return one of two modules back to Earth. COMET provides basic utilities such as electric power, a tightly controlled thermal environment, attitude control, data management and communications while in orbit. COMET is a two part Free Flyer, which will carry experiments into a low Earth orbit. The Free Flyer consists of a Service Module and a Recovery System. The Recovery System returns to Earth by parachute after thirty days in orbit. The Service Module continues in orbit for up to two years.The thermal control requirements for COMET provide special and unique challenges for the thermal system design and integration of the Service Module satellite. The Service Module is required to maintain the experiment payload environment at 22.2°C ± 2.8°C on the launch pad, during launch, and for two years after orbit insertion. The thermal control system is required to operate in a micro-gravity environment of less than 10 micro-g from orbit insertion until mission completion. Other thermal system design drivers include the Earth and sun satellite orientations, ground testing, distributed system integration and testing, launch pad experiment payload and housekeeping equipment accessibility, and thermal system failure detection and recovery scenarios.This paper describes the COMET Service Module spacecraft configuration design and integration with a CPL system. The service module thermal control system design uses a CPL to maintain the experiment payloads at 22.2°C ± 2.8°C, and a passive thermal control to maintain the housekeeping equipment at its operating conditions.