Built to withstand temperatures up to 2500 degrees F, Solar Probe Plus will study the origins of the solar wind.
At its very closest approach of only 3.8 million miles from the Sun’s surface, SPP will be subjected to up to 475 times the solar irradiance experienced at Earth. Thus, the science collection phases of the mission during close encounters are designed to be autonomous. That is, without real-time direction from ground-controllers.
Data taken during these collection phases will be saved on solid state recorders for subsequent downlink via a high gain antenna pointed back to Earth. .
The probe’s thermal protection system is an 8-foot-diameter, 4.5-inch-thick, carbon-carbon, carbon foam shield that sits atop the spacecraft. Basically, most of the entire spacecraft “hides” behind this shield during the spacecraft’s closest approach to the Sun, says McNutt.
“The solar arrays do retract and there is a battery,” said McNutt. “But even at [closest approach], part of the arrays remain illuminated to provide power.”
McNutt notes that an active water circulation system from the back of the solar arrays to radiator panels which keep the arrays cool, a first for any spacecraft. He says the mission’s science goals focus on tracing the flow of energy that heats the solar corona and accelerates the solar wind. Nagging questions include whether the sources of the solar wind steady or intermittent and the mechanisms that accelerate and transport the Sun’s energetic particles.
In an effort to answer such questions, SPP will sample the solar wind during rising solar activity, while also directly imaging the Sun’s corona.