Mapping out the heliosphere, Earth’s protective bubble
Photos by Evan Krape and courtesy of NASA/Kim Shiflett September 18, 2025
UD’s Matthaeus helps shape NASA’s IMAP mission, launching this month
Editor's note: NASA and SpaceX are now targeting Wednesday, Sept. 24, at 7:30 a.m. for the launch of NASA and the National Oceanic and Atmospheric Administration (NOAA) space weather missions.
Much as we may treasure and proclaim our independence, we actually live in a protective bubble called the heliosphere.
This extraordinary environment is basically the sun’s sphere of influence. It surrounds our solar system and shields it from galactic cosmic radiation that comes mostly from outer space — rays that travel near the speed of light. The Earth’s magnetic field also protects us from incoming radiation.
The heliosphere is an electro-magnetic environment, inflated by the solar wind — the stream of high-energy particles (protons, ions and electrons) that the sun constantly shoots out at speeds often greater than 1 million miles per hour.
We’re about to learn much more about this region, when NASA’s IMAP (Interstellar Mapping and Acceleration Probe) spacecraft is launched on a SpaceX Falcon 9 rocket next week from Kennedy Space Center in Florida. IMAP has a suite of 10 instruments that will measure the solar wind, plasma, high-energy particles and electromagnetic fields for monitoring space weather, which can have great impact on astronauts, satellites and telecommunications systems.
One of our planet’s great experts on the heliosphere and the solar wind is William H. Matthaeus, the Martin Pomerantz Professor of Physics and Astronomy at the University of Delaware. Earlier this year, Matthaeus was elected to membership in the National Academy of Sciences, one of the highest honors a scientist can receive.
Matthaeus helped to shape the scientific questions, calculations and specifications related to the magnetic field instrument that laid the foundation for IMAP and is a co-investigator. His primary contributions relate to magnetic field turbulence near the Earth, plasma velocities and temperatures near the Earth.
During its two-year journey, IMAP will investigate two primary issues — how the charged particles from the sun get so much energy and how the entire solar system interacts with interstellar space. It will also measure and study the fine particles known as cosmic dust that originates from outside the solar system.
The project, led by Princeton University’s Professor David J. McComas and managed by the Johns Hopkins Applied Physics Laboratory, also includes other universities and industries from around the U.S., 82 partners in all.
“We are going to find incredible new discoveries,” said Nicky Fox, associate administrator for NASA’s Science Mission Directorate, during a media briefing earlier this month. “What is coming from the sun? What is coming from the interstellar medium? We’re excited about the applications.
“But the actual discovery science is going to literally rewrite textbooks and that’s why we’re so excited about it.”
Matthaeus agrees.
“We intend to be part of that rewrite,” Matthaeus said, “not just me, but my students and postdocs. I always tell them, ‘Don’t just look over your shoulder. Try to do something nobody else has done before.’”
Tagging along with IMAP are two “rideshare” missions — the Carruthers Geocorona Observatory and NOAA’s Space Weather Follow On L1 spacecraft. That L1 part of that name refers to the address IMAP will have in the heliosphere — Lagrange Point 1 — located about 1 million miles from Earth (toward the sun) in an area of relative equilibrium, where the gravitational forces of the sun and the Earth are about even. That makes for an efficient spacecraft “parking spot” to capture measurements over a longer period. It also could provide about a half hour’s warning of incoming harmful radiation.
The Carruthers Geocorona Observatory is the first mission focused on studying changes in the exosphere, the Earth’s outermost atmosphere. The NOAA mission will measure the solar wind, thermal plasma and the magnetic field and be able to detect coronal mass ejections, giant eruptions from the sun’s surface, which send space weather toward Earth.
“That all relates to space weather,” Matthaeus said. “If you want to know what’s hitting the Earth, you have to have spacecraft in the right position. That’s always of interest from a space weather point of view. You get to understand how significant the perturbations are when they come by. That’s important if you want to design missions to better withstand the conditions and see conditions farther from the sun.”
It's essential for the protection of astronauts who may be involved in upcoming missions to the moon or Mars.
The L1 region is of special interest to Matthaeus, too. He wants to know which other spacecraft may be nearby. Multispacecraft measurements are important for understanding the dynamics of plasma, for example, and seeing more dimensions of all that is happening in the region.
“Making simultaneous measurements from multiple spacecraft tells you information that is not available any other way,” he said. “That’s one of the specialties of our group. And IMAP is going to add another spacecraft to the L1 fleet, what I like to call the ‘L1 constellation.’”
In addition to IMAP, other data-gathering spacecraft in the neighborhood could be Ace, Wind, Discover, MMS, Aditya.
“There will be at least six spacecraft available simultaneously,” he said. “You can’t measure three dimensions with one spacecraft. And even with two, you only get one direction. Now we’ll have information about the three-dimensional structure of shocks, coronal mass ejections and turbulence. It’s going to be an enormous data science problem. But it’s very exciting and it’s going to pose new challenges.”
That, he said, is his No. 1 interest in the mission.
“Once you have this many spatial points, over time, now you can start separating space and time. And that’s important. That allows you to measure things like the decay rate of the turbulence and the heating rate of the turbulence.”
Among the special capacities of IMAP is its ability to capture images of energetic neutral atoms (ENAs). Three of its 10 instruments will capture these atoms, which — because they have no charge — travel in a straight line, unaffected by magnetic fields and their turbulence. The goal is to study where these atoms come from to better understand distant regions of space.
NASA has a video on its YouTube channel that further explains the IMAP mission.
How to watch the launch
The launch of the IMAP spacecraft is planned for 7:32 a.m. Tuesday, Sept. 23. Live coverage is available at these sites:
Also available on the NASA app on Apple TV and Roku
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