PUNCH News & Nuggets

Heliophysicists have produced the first continuous, two-dimensional maps of the Sun’s Alfvén surface – the region of space where the solar wind irrevocably escapes the grip of the Sun’s magnetic field – and demonstrated the dynamical variation of its properties as our star moves through its activity cycle. Beyond this boundary, the speed of outflowing solar material becomes faster than the speed of magnetic waves, marking an effective outer “edge” of the solar atmosphere. Published in The Astrophysical Journal Letters (Badman et al. 2025) and co-authored by PUNCH Co-I Rohit Chhiber, the study employed a combination of in-situ measurements and magnetic models from several space missions spanning a range of distances from the Sun, to infer the location of the Alfvén surface in the Sun’s equatorial plane, thereby providing a “top-down” view (looking downwards from above the solar system) of its probable shape. Tracking the surface’s evolution from 2018 (when the Sun was dormant) to 2025 (when it was highly active) revealed that its distance from the Sun, its thickness, and its “spikiness” increased with solar activity.

On 11-Mar-2025, PUNCH launched into Sun-synchronous polar orbit on a Falcon 9 spacecraft, in a rideshare with the SPHEREx mission. In the 365 days since then, PUNCH has downlinked ~1.5 million images from space, tracked over 100 CMEs, observed several new comets and one interstellar visitor, and changed the way humanity sees our environment in space. We are still refining the data processing for the most complex ground pipeline produced for any Explorer mission, but the images are already spectacular. Get ready for an amazing year of PUNCH science results ahead!

Polarization puts the "P" in PUNCH! The ratio of radially to tangentially polarized Thomson-scattered white light provides a powerful tool for locating the 3D position of compact structures in the solar corona and inner heliosphere, and PUNCH has been designed to take full advantage of this capability.

The Polarimeter to Unify the Corona and Heliosphere (PUNCH) is a complicated mission to do a very simple thing: image the entire outer corona and inner heliosphere, all the time, in 3D. This overview paper describes the entire design arc: the motivating science, the mission science requirements and their definition process, the mission design, the instrumentation, the data products and analysis tools, and at least some additional science enabled by PUNCH.

Late November through late January is the darkest time of year in Earth’s northern hemisphere, as Earth’s axis points away from the Sun, making nights longer and days shorter. PUNCH experiences the seasons too: during these dark days, each spacecraft spends a few minutes per orbit passing through Earth’s shadow (and experiencing a brief “night”). This plot shows the state of charge of all four satellites’ batteries over the ten-week “eclipse season”, highlighting that even orbiting spacecraft experience the same astronomical calendar that we do.

final integration and testing on the Narrow Field Imager (NFI) in a cleanroom facility. The red hardware components are protective covers that were removed before flight. Detailed diagram showing the compact design of the Narrow Field Imager (NFI). The cut-away view illustrates the internal components, including baffles, heat rejection mirror, and the optical lens assembly which are all configured to image the faint light of the corona to the camera. The Narrow Field Imager (NFI), the coronagraph for NASA's PUNCH mission, images the innermost part of the PUNCH field of view. It was delivered about eight months before launch, and successfully met all pre-launch requirements in testing. NFI is an example of a new class of “compact” coronagraphs developed at the Naval Research Laboratory, with a single stage of external occultation to observe the faint solar corona with a small form factor.

PUNCH CONNECT (COmmunity Nexus for Noteworthy Event Context and Tracking) is a new topical focus group open to the community, dedicated to identifying solar and heliophysical events that benefit from cross-mission activities.