NASA’s PUNCH constellation of small satellites predicted the arrival time of a solar eruption at Earth to within 30 minutes, in a first test of the mission’s space weather forecasting capability. The agency, which released the results on August 4, said that precision is about 10 times better than the current state of the art, shrinking the arrival window from roughly 5 hours to half an hour. The findings were presented at the Committee on Space Research (COSPAR) scientific meeting and are under review at the journal Space Weather.
PUNCH, short for Polarimeter to Unify the Corona and Heliosphere, is a network of four small satellites launched in 2025. The spacecraft take continuous 3D images of the inner solar system, capturing a new picture every 4 minutes, and their wide field of view lets them track coronal mass ejections, the large explosions of solar material known as CMEs, nearly all the way to Earth. Before the mission, CMEs could only be observed while crossing about one-fifth of the distance from the Sun to Earth, leaving forecasters to guess what happened over the remaining span.
The test used a CME that left the Sun on May 31, 2025. According to NASA, PUNCH images were fed into a computer model that analyzed the CME’s leading edge over time and, using its speed and geometry, calculated when the eruption would reach Earth. About 12 hours after the CME left the Sun, the model settled on a final prediction, with arrival due roughly 8 hours later. The model also flagged when its estimate had stabilized, a feature that could give forecasters confidence in a live warning.
Science, which reported the result the same day, adds detail: the storm that followed was classed as a G4 geomagnetic event, and the PUNCH-based models placed its arrival at Earth between 5:00 and 5:30 a.m. GMT on June 1, representing roughly 8 hours of advance notice for operators of satellites and power grids. Craig DeForest, PUNCH’s principal investigator at Southwest Research Institute, called the outcome stunning and compared the improvement to moving from a steam engine to a modern internal combustion engine.
The result is a proof of concept on a single event, not an operational forecasting service. The analysis was retroactive, the team used a deliberately simple model of the CME’s evolving shape, and the manuscript has not yet cleared peer review. NASA said scientists think more refined PUNCH data and better models could push arrival forecasts further in advance than the roughly 12-hour post-eruption timeline achieved in this test. The team is also analyzing dozens of other CMEs that PUNCH has tracked, and forecasters are testing a faster product called QuickPUNCH that uses slightly lower quality images.
The imagery is producing other findings as well. High-resolution views show CME clouds are clumpier than previously thought and keep evolving as they cross the solar system, a clue about how plasma moves through space, including in regions where it cannot be studied on small scales, such as the gas clouds where stars form.
Sources
- NASA Science: https://science.nasa.gov/science-research/heliophysics/nasas-punch-sharpens-solar-storm-forecasting-in-first-test
- Science (AAAS): https://www.science.org/content/article/nasa-mission-predicts-solar-explosion-s-arrival-earth-stunning-precision