Thermal Stability Testing of Two-Phase Thermal Control Hardware for the Surface Water Ocean Topography Mission

The thermal architecture for the Surface Water Ocean Topography mission utilizes loop heat pipes and constant conductance heat pipes to transport waste heat (> 1000 Watts) from the instrument electronics to the radiator. The main thermal design risk is the ability to maintain a temporal stability of <0.05 Celsius per minute in a low earth orbit environment. The stringent thermal requirements are part of the overall error budget needed to meet the primary mission science objectives. A testbed was developed to simulate flight-like loads and environments in order to validate the thermal subsystem can meet the temporal stability requirements. Preliminary testing showed that the thermal control system can meet the stability requirement and that loop heat pipes are actually helping to maintain stability during transient sink temperature changes for this specific flight application and boundary conditions.