Polarimeter to Unify the Corona and Heliosphere

The stated primary objective by PUNCH's mission is "to fully discern the cross-scale physical processes, from microscale turbulence to the evolution of global-scale structures, that unify the solar corona and heliosphere".[5] In other words, the mission aims to understand how the solar corona becomes the solar wind.[6]

The two specific goals are to understand how coronal structures become the ambient solar wind, and to understand the dynamic evolution of transient structures in the young solar wind.[5] The Principal Investigator, Craig Edward DeForest from Southwest Research Institute (SwRI), thinks that such closer study will also lead to a better understanding of the causes of solar weather events like coronal mass ejections (CMEs), which can damage satellites and disrupt electrical grids and power systems on Earth.[3]·[2]

The more we understand what drives space weather and its interaction with the Earth and lunar systems, the more we can mitigate its effects – including safeguarding astronauts and technology crucial to NASA's Artemis program to the Moon.[7]

The mission configuration consists of a constellation of four observatories, each carrying one instrument.[8]

• The Narrow Field Imager (NFI) sits on only one spacecraft, and is an externally occulted visible-light coronagraph.
• The Wide Field Imagers (WFIs) are side-looking heliospheric imagers with planar-corral baffles that sit on the remaining 3 spacecraft.

The fields of view of the 3 WFIs overlap slightly with each other and with the NFI, and the instruments' operation is synchronized. The instruments operate through polarized Thomson-scatter imaging of the transition from corona to heliosphere.[9] PUNCH integrates images from its constellation of small satellites into a global composite after each orbit, covering ~6 orders of magnitude dynamic range. Through a stream of these images, PUNCH achieves 3D feature localization and accurate deep field imaging.[10] The mission builds on CYGNSS experience with smallsat constellations.[11]

Phase B will last nearly a full year. Throughout the process, SwRI will collaborate with the U.S. Naval Research Laboratory (NRL) and the Rutherford Appleton Laboratory in Oxfordshire, England.

PUNCH, which will operate in low Earth orbit, will work in synergy with NASA's Parker Solar Probe and the ESA's Solar Orbiter.[3]·[9]