NASA is developing a fortified satellite that will nearly touch the sun starting in 2018, collecting unprecedented data on the super-heated solar atmosphere.

Artist's concept of Solar Probe Plus. Credit: JHU/APL

The space agency announced this week five experiments for the Solar Probe Plus mission, all from U.S. government and academic institutions.

Scheduled for launch in August 2018, Solar Probe Plus will dive into the outer corona and approach within 4 million miles of its surface in a series of low passes sweeping closer to the sun than any other spacecraft has ever visited.

"The experiments selected for Solar Probe Plus are specifically designed to solve two key questions of solar physics -- why is the sun's outer atmosphere so much hotter than the sun's visible surface and what propels the solar wind that affects Earth and our solar system?" said Dick Fisher, director of NASA's heliophysics division. "We've been struggling with these questions for decades and this mission should finally provide those answers."

After its launch from Earth, Solar Probe Plus will orbit the sun at least 24 times and repeatedly sample the sun's outer atmosphere, where temperatures reach more than 2,500 degrees Fahrenheit.

Weighing about 1,350 pounds, the satellite will be shielded by a carbon-composite about 4.5 inches thick and 8 feet in diameter. The heat shield will help the probe withstand solar intensities 500 times greater than what satellites at Earth experience.

No spacecraft has ever encountered the hazardous radiation and dust environment that Solar Probe Plus will traverse.

The Johns Hopkins University Applied Physics Laboratory is building the spacecraft and will operate the mission for NASA.

The objectives of Solar Probe Plus include studying the dynamics of the sun's magnetic field, unraveling the forces that drive the solar wind and observe energy transport mechanisms.

"This project allows humanity's ingenuity to go where no spacecraft has ever gone before," said Lika Guhathakurta, Solar Probe Plus program scientist at NASA Headquarters. "For the very first time, we'll be able to touch, taste and smell our sun."

Solar Probe Plus could enter its Phase B definition phase next year.

NASA is investing $180 million in five investigations that will collect data aboard the Solar Probe Plus spacecraft. They include:

• Solar Wind Electrons Alphas and Protons Investigation from the Smithsonian Astrophysical Observatory in Cambridge, Mass. This instrument will count electrons, protons and helium ions in the solar wind and measure their properties.
  
  
• Wide-field Imager from the Naval Research Laboratory in Washington, D.C. This payload will make three-dimensional images of the sun's corona, solar wind and shocks around the spacecraft. The Wide-Field Imager will image the plasma Solar Probe Plus's other instruments directly sample.
  
  
• Fields Experiment from the University of California Space Sciences Laboratory in Berkeley, Calif. This investigation 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.
  
  
• Integrated Science Investigation of the Sun from the Southwest Research Institute in San Antonio. This payload consists of two instruments that will monitor electrons, protons and ions that are accelerated to high energies in the sun's atmosphere.
  
  
• Heliospheric Origins with Solar Probe Plus led by principal investigator Marco Velli of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Velli 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.