https://phys.org/news/2018-06-particles-deep-space-nasa-balloon.html

The science driving this investigation is a search for the source of ultra-high energy particles from space that hit our Earth. One type of these particles is cosmic rays: sub-atomic nuclei traveling from every direction in space, accelerated by supernovas and other unknown cosmic phenomena. Similarly mysterious are neutrinos, the "ghost particles" that pass through us all the time, mostly undetected.

While there is much we don't know about neutrinos, the most pressing concern is where they come from. All that is known is that, based on studies at the Pierre Auger Observatory in Argentina, the most energetic cosmic rays that hit the Earth are coming from beyond our own galaxy. The most extreme cosmic rays and neutrinos offer the most clues to their origins and travels because they can resist the effects of magnetic fields in space that curve the paths of weaker particles. These are what this new NASA-funded balloon experiment will be hunting.