Two puzzles about the Sun continue to defy explanation more than half a century after their discovery. Why is the atmosphere of the Sun, or corona, thousands of times hotter than the surface of the Sun beneath it? And how is a fraction of the Sun's atmosphere accelerated to escape as the solar wind? The best way to understand what causes the observed heating and acceleration is to send a probe directly into the solar corona, and advances in technology and mission design have finally made this possible.

Solar Probe Plus is a NASA mission designed to plunge directly into the atmosphere of the Sun for the first time in history. Reaching 4 million miles from the surface of the Sun, the spacecraft will enter a completely unexplored region of space. At these distances the Sun will be over 500 times brighter than it appears at Earth and particle radiation from solar activity will be harsh. In order to survive the spacecraft folds its solar panels into the shadows of its protective solar shade, leaving just enough of the specially-angled panels in sunlight to provide power closer to the Sun

The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation is the set of instruments on the spacecraft that will directly measure the properties of the plasma in the solar atmosphere during these encounters. A special component of SWEAP is a small instrument that will look around the protective heat shield of the spacecraft directly at the Sun. This will allow SWEAP to sweep up a sample of the atmosphere and touch the Sun, our star, for the first time.

The SWEAP Investigation is lead by Dr. Justin C. Kasper of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. Institutions participating in SWEAP include the University of California, Berkeley Space Sciences Laboratory, the NASA Marshall Space Flight Center, the University of Alabama Huntsville, NASA Goddard Space Flight Center, Los Alamos National Laboratory, University of New Hampshire, and the Massachusetts Institute of Technology.

This is the main web page for the SWEAP Investigation. Follow the links in the navigation bar on the left in order to learn more about the SWEAP science team, the instruments, and our science. Join us on our adventure to touch the Sun by following our Twitter feed @TheSWEAPLife.