Thermal Performance of Parker Solar Probe through Orbit Eleven

The Parker Solar Probe (PSP) spacecraft has successfully completed eleven of 24 solar orbits that have explored the inner region of the heliosphere through in-situ and remote sensing observations of the Sun's magnetic and electrical fields, plasma, and accelerated particles. During the first four years of the 7-year primary mission that launched on 12 August 2018, the spacecraft has experienced a wide range of hot and cold thermal environments. So far, PSP has performed nominally during the eleven perihelion encounters and the five Venus fly-bys that have included two 11-minute eclipses. The extreme solar constant experienced during the mission minimum perihelion required the development of two revolutionary technologies: (1) to actively cool photovoltaic solar arrays and (2) to passively protect the spacecraft from the intense solar heating without changing shape or insulating performance when the sun-side temperature reaches nearly 1000 °C. The maximum heating from the Sun's corona region, when the spacecraft reaches the minimum perihelion distance of 9.86 solar radii (RS / ~475 suns), will occur during the final three orbits. Key to spacecraft electric power generation and overall mission success are the actively cooled photovoltaic solar arrays that use thermally conditioned water provided by the state-of-the-art Solar Array Cooling System (SACS) and state-of-the-art construction of the Thermal Protection System (TPS) that utilizes C-C foam sandwiched between C-C face sheets to create the very large structurally ridged and thermally insulating packaging umbra for the rest of the spacecraft below. This paper will discuss the thermal performance of the SACS and the passively cooled spacecraft during Orbit 11, when the spacecraft reached a minimum solar distance of 13.28 RS (~262 suns), and compare this performance to that previously measured during the first ten orbits.