PUNCH Spacecraft’s Last Countdown: The Final Preparations Before Takeoff!

Four compact suitcase-sized spacecraft, crafted by Southwest Research Institute, have made a concluding Earth-side stop at Vandenberg Space Force Base in California. NASA’s Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is hitching a ride to space with the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) observatory.

“The PUNCH mission will enhance our comprehension of the sun’s corona, the external atmosphere observable during total solar eclipses, along with the ‘solar wind’ that fills and characterizes the solar system,” stated PUNCH Principal Investigator Dr. Craig DeForest of SwRI’s Solar System Science and Exploration Division. “Once the constellation is set up, we’ll be capable of routinely observing and grasping the solar wind itself as it streams from our star and flows over Earth.”

The PUNCH constellation of satellites aims to launch in late February 2025 into a polar orbit along the day-night line, ensuring that the spacecraft remain in sunlight with an unobstructed view in all directions.

Three satellites will feature SwRI-developed Wide Field Imagers (WFI)—heliospheric imagers offering views from 18 to 180 solar radii, or 45 degrees, away from the sun in the sky. The WFIs utilize an artificial “horizon” and deep baffles to observe the extremely faint outermost segment of the solar corona and the solar wind itself.

“The instrument diminishes direct sunlight by over 16 orders of magnitude or a factor of 10 million billion—the comparative ratio between the mass of a human and the mass of a cold virus,” DeForest mentioned. “The wide-field achromatic optics draw upon the renowned Nagler eyepiece design utilized in terrestrial telescopes.”

One satellite is equipped with a coronagraph, the Narrow Field Imager developed by the U.S. Naval Research Lab, which continuously images the sun’s corona.

All four spacecraft are coordinated to function as a single “virtual instrument” to capture approximately a quarter of the sky, centered on the sun. Each spacecraft also incorporates a camera, developed by RAL Space, to gather three raw images through three distinct polarizing filters every four minutes. Additionally, each spacecraft will produce a clear, unpolarized image every eight minutes for calibration purposes.

“When electron particles disperse sunlight, the light waves become aligned in a particular manner—this is polarized light,” DeForest explained. “By assessing the light using polarizing filters similar to polarized sunglasses, PUNCH scientists can create a 3D representation of the features they observe throughout the corona and inner solar system.”

This fresh perspective will enable scientists to identify the precise path and velocity of coronal mass ejections as they traverse the inner solar system, enhancing the capabilities of current instruments which only analyze the corona itself and cannot detect motion in three dimensions.

“The PUNCH team has displayed exceptional resilience as we efficiently tackled numerous last-minute challenges over recent months to finalize integration and environmental testing of the four observatories,” remarked PUNCH Project Manager Ronnie Killough. “I am eager for a successful launch.”