https://phys.org/news/2018-11-nasa-team-first-ever-coronagraph-formation.html

The scientific instrument on the BITSE mission, which also involves the Korea Astronomy and Space Science Institute, is a coronagraph. These devices block the Sun's bright surface to reveal its faint, but very hot upper atmosphere called the corona.

However, the BITSE coronagraph has added features that can measure some very important properties of the solar wind, which can travel as fast as a million miles per hour as it flows off the Sun carrying charged particles or plasma and embedded magnetic fields outward across the solar system. Although scientists know that the solar wind originates in the corona, they don't know precisely how it forms or accelerates.