NASA launches twin satellites to spy on the invisible shield that protects Earth

On July 23, 2025, the National Aeronautics and Space Administration NASA launched two satellites called TRACERS from Vandenberg Space Force Base in California. The pair will study the invisible magnetic shield that surrounds Earth and track the bursts of energy that force their way through it.

Flying about 360 miles above Earth, the two craft will chase each other through a gap in the magnetic field near the pole. Their goal is to capture detailed snapshots of a process that helps drive solar storms and disrupt technology.

TRACERS and the magnetosphere

The TRACERS mission, short for Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites, is led by David Miles, principal investigator at the University of Iowa. He studies how Earth’s magnetic environment responds to activity from the Sun.

Earth is wrapped in a magnetosphere, a bubble of magnetic field that shields the planet. Without it, the charged particles from the Sun would erode the atmosphere much faster and make life harder.

Stormy conditions in this region are called space weather, changes in near Earth space that can disturb technology and communications.

Strong space weather can interfere with satellite navigation signals, radio links, and even power lines on the ground.

All of this trouble starts with the solar wind, a stream of charged particles constantly blowing outward from the Sun. When this flow hits Earth’s magnetic field, some of the energy flows into the system and can rush toward our planet.

Earth’s magnetic reconnection

The process that lets solar wind energy enter the magnetosphere is called magnetic reconnection, a rearranging of magnetic field lines that releases energy.

When reconnection happens, field lines snap apart and join again, sending charged particles toward Earth at high speeds.

Scientists now know that this process is the primary way the solar wind transfers energy into Earth’s magnetic field and powers geomagnetic storms.

Those storms can light up the sky with auroras and also disturb satellites and power systems when conditions align.

The tricky part is that reconnection does not fire at a steady rate, which makes space weather far harder to predict than ordinary storms.

Knowing when and how it turns on gives scientists a better chance to warn operators of satellites, power grids, and communication networks.

“TRACERS is set to transform our understanding of Earth’s magnetosphere,” said Miles. The mission is designed to catch reconnection in action repeatedly, giving researchers a clear timeline instead of single snapshots.

TRACERS satellites watch the cusp

The twin craft fly through the polar cusp, a gap in Earth’s magnetic field near the pole. This region lets some of the solar wind reach the upper atmosphere directly, which makes it a natural laboratory for reconnection.

In their science mission, the two spacecraft will pass through this region more than 3,000 times in about one year. They fly in the same orbit only tens of seconds apart, which helps separate quick changes in time from differences in space.

As the pair cuts through the cusp, their instruments record magnetic fields, electric fields, and swarms of charged particles flowing into the upper atmosphere.

There the ionosphere, a layer of the atmosphere filled with charged particles, reveals where energy from space is landing.

By lining up data from both satellites, scientists can see whether changes in the cusp move with the solar wind or pulse in time.

That comparison answers a long standing question in space physics about whether reconnection is mostly patchy in space or beating in time.

Small companions with big jobs

Riding on the same rocket as TRACERS, a satellite called Athena EPIC, short for Economical Payload Integration Cost, is testing a flexible commercial design.

Once its systems are checked, Athena EPIC will spend a year measuring heat leaving Earth with instruments that support better climate and weather models.

Another passenger, the Polylingual Experimental Terminal PExT experiment, is testing a terminal that can communicate with both government and commercial networks in orbit. 

The PExT terminal uses software defined radios to switch between systems automatically so future spacecraft can stay connected without relying on a single network.

A third small mission, Relativistic Electron Atmospheric Loss (REAL), focuses on the Van Allen radiation belts, doughnut shaped regions filled with energetic trapped particles. 

This CubeSat carries a sensitive particle detector that tracks energetic electrons falling from the Van Allen belts and helps protect vulnerable satellites.

A CubeSat, a standardized small satellite about the size of a shoebox, gives researchers a way to test focused ideas without the cost of a large mission.

By sharing the launch with TRACERS, these smaller projects collect data while adding context to what is happening in near Earth space.

Lessons from TRACERS

TRACERS joins NASA’s broader heliophysics program, the study of how the Sun influences space. That program uses many spacecraft to watch our star and track its effects on Earth’s space environment.

“NASA’s heliophysics fleet helps to safeguard humanity’s home in space,” said Joe Westlake, heliophysics division director at NASA Headquarters in Washington.

That focus on protection runs through TRACERS, which looks directly at how energy from the Sun interacts with Earth’s magnetic shield.

“NASA is proud to launch TRACERS to demonstrate and expand American preeminence in space science research and technology,” said acting NASA Administrator Sean Duffy.

The TRACERS team works with other NASA missions that watch reconnection and connect local measurements near Earth with wider space weather patterns.

As data from TRACERS, Athena EPIC, PExT, and REAL start to flow, scientists will see how different pieces of Earth’s space environment fit together.

What they learn about this invisible shield will protect satellites and astronauts and support future journeys to the Moon and Mars.

Image credit: SpaceX

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