The Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Maryland has designed the Solar Probe Plus. They will also build and operate it for NASA. The mission recently passed a crucial milestone. It successfully completed its Critical Design Review, or CDR. During this process, NASA certified that the Solar Probe Plus mission design has reached the advanced stage and gave APL the green light to begin building, testing, and assembling all of the mission's elements. Essentially the project is moving from the drawing board to the factory floor.
The Solar Probe Plus is scheduled to launch from the Cape Canaveral Air Force Station in Florida atop a Delta 4-Heavy rocket. Over the course of six years, the probe will make 24 elliptical orbits of the Sun. Each orbit will bring it closer to the Sun. To keep from being pulled in to the Sun's immense gravity well, the Solar Probe Plus will have to be going very fast. Using seven gravity assist flybys of Venus, the probe will eventually accelerate to 125 miles per second or 0.067% the speed of light. As its speed increases Solar Probe Plus' distance from the Sun will decrease. The closest three orbits will bring the craft within a mere 3.8 million miles from the surface of the Sun. This may not seem all that close, but keep in mind that this will actually bring the Solar Probe Plus into the Sun's corona, its outer atmosphere, where it will face temperatures of 2500 degrees Fahrenheit.
Solar Probe Plus will carry four sets of instruments that will allow it to study magnetic fields, plasma, and energetic particles, and will image the solar wind. The craft and its instruments will need protection from the Sun's searing heat and radiation. To this end, it will be protected by a 4.5-inch-thick carbon-composite shield. This will allow the Solar Probe Plus to complete its observational odyssey before eventually meeting its fiery end.
(Source: NASA)