Parker Solar Probe Solar Array Cooling System In-Orbit Performance Review
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After years of development, Parker Solar Probe (PSP) was launched on August 12, 2018 starting its seven-year journey to unveil the long-sought mystery of our solar system. The in-situ measurements and imaging, powered by a pair of solar array wings, will be used to understand how the sun's corona is heated and how the solar wind is accelerated. As the PSP orbits close to the sun, the cooling system removes the excess heat from the solar cells to prevent them from overheating. UTC Aerospace Systems (UTAS) started the development of the Solar Array Cooling System (SACS) in late 2008. After extensive studies, a single phase mechanical pump flow loop with water as the working fluid was selected due to the unique operating environment of the PSP. Although it is an excellent heat transfer fluid, water has a major disadvantage: its high freezing point. A unique operating strategy involving two activations and multiple hot slews was developed to prevent the water from freezing throughout the whole mission. The PSP SACS hardware includes two pumps and two motor controllers (one primary and one redundant), one accumulator, two Solar Array Platens (SAPs), four Cooling System Primary Radiators (CSPRs), three isolation valves, three service valves, and instruments. In November 2013, the PSP SACS completed the half scale thermal vacuum tests and achieved TRL 6 advancement. The subsequent full scale SACS thermal-vacuum test and the post-integration observatory level thermal-vacuum test were completed in March 2017 and February 2018, respectively. The PSP SACS has been operating successfully through four major operating points; the first activation, trajectory correction maneuvers, the second activation, and the first perihelion. This paper reviews PSP SACS hardware, the responses of PSP SACS at the aforementioned four operating points, and the overall performance of the PSP SACS in its early mission.