Solar Probe Plus Mission Overview

Solar Probe Plus will be the first mission to pass into the solar corona to study how the corona is heated and the solar wind is accelerated. Solving these two fundamental mysteries has been a top-priority science goal for over five decades. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, is managing the mission for NASA’s Living with a Star Program, including the development, build, and operation of the spacecraft. SPP will launch in 2018, performing 24 orbits of the Sun over a 7-year duration. The mission design utilizes seven Venus gravity assists to gradually reduce perihelion from 35 solar radii in the first orbit down to 9.86 solar radii for the final three orbits. Science data are collected during each perihelion pass and transmitted to Earth between passes. The SPP spacecraft is 665-kg at launch, almost 3 meters in height and 2.3 meters in diameter. A thermal protection system composed of Carbon-Carbon and carbon foam protects the spacecraft from the extreme solar environment near perihelion. At 9.86Rs, the solar intensity is 475 times that at 1AU. Hiding behind the thermal protection system provides the spacecraft a benign thermal environment while the TPS experiences temperatures of 1400°C on its sun-facing surface. Solar Probe Plus is solar powered with water cooled solar arrays for power generation that maintain the solar cell assemblies within their required temperature limits. This paper presents the science overview, mission concept, and spacecraft description as the mission approaches its Preliminary Design Review.