The Solar Probe Plus spacecraft is being designed and build by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Current concept of the Solar Probe Plus spacecraft.

The compact, solar-powered probe will weigh about 1,350 pounds; preliminary designs include an 8-foot-diameter, 4.5-inch-thick, carbon-carbon, carbon foam solar shield atop the spacecraft body. The solar arrays will retract and extend as the spacecraft swings toward or away from the Sun during several loops around the inner solar system, making sure the panels stay at proper temperatures and power levels. At its closest passes the spacecraft must survive solar intensity more than 500 times what spacecraft experience while orbiting Earth. Check out the spacecraft web page at JHU/APL for more details.

There are five scientific investigations for Solar Probe Plus. They are:

• Solar Wind Electrons Alphas and Protons (SWEAP) Investigation. This is our investigation and you can learn about it by exploring these web pages. The purpose of SWEAP is to scoop up samples of the atmosphere of the Sun during each of the encounters. SWEAP measures the detailed properties of electrons, protons, and helium ions, the main components of the corona and solar wind. Principal Investigator: Justin C. Kasper, Smithsonian Astrophysical Observatory, Cambridge, Mass.


• The Fields Experiment. FIELDS will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the sun's atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft's antenna. Principal Investigator: Stuart Bale, University of California Space Sciences Laboratory, Berkeley, Calif.


• Integrated Science Investigation of the Sun. This investigation consists of two instruments that will monitor electrons, protons and ions that are accelerated to high energies in the sun's atmosphere. Principal Investigator: David McComas of the Southwest Research Institute in San Antonio.


• The Wide-field Imager, a telescope that will make 3-D images of the sun's corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft providing direct measurements by imaging the plasma the other instruments sample. Principal Investigator: Russell Howard, Naval Research Laboratory, Washington


• Heliospheric Origins with Solar Probe Plus. Principal Investigator: Marco Velli, of NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the mission's observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.