🚀 Space Radiation Basics - Part II
An Introduction to Trapped Particles
I’m always amazed by how much there is still to learn. Imagine those first engineers working on Sputnik 1, facing challenges no one had ever solved before. Today, we’re living through a new space revolution—and “how do we do this?” is a question that keeps coming back.
To succeed and offer the best possible solutions, we need to understand the problems deeply. Space is a harsh place, and we often forget how protective Earth really is. Our planet shields us from enormous amounts of energy—something Mars or the Moon can’t do. That’s a challenge every satellite (and future astronaut) must face.
Let’s unpack what this means.
🌌 What Is Space Radiation?
Radiation is a form of energy that travels through space as rays, electromagnetic waves, or high-speed particles. Space is full of it. These particles come from every corner of the galaxy—and even farther.
Here on Earth, we don’t notice most of this radiation because our atmosphere and magnetic field protect us. But as you rise into the sky, that protection decreases. Flying in a plane exposes you to more radiation. In Low Earth Orbit (LEO), it gets even worse.
So let’s understand how Earth protects us—and what happens when we leave that protection behind.
🌍 Earth’s Magnetosphere
You’ve probably used a compass or noticed the one on your phone or smartwatch. That works thanks to Earth’s magnetic field, known as the magnetosphere. It’s not just useful for navigation—it also acts as a powerful shield.
The magnetosphere deflects much of the space radiation that hits our planet. Without it, life as we know it wouldn't exist. Mars, for example, lacks a strong magnetic field, which makes it far more vulnerable to radiation—something we’ll need to solve before we can live there.
Credits: NASA/Goddard/Aaron Kaase
đź”—For a deeper explanation visit: https://pwg.gsfc.nasa.gov/Education/wtrap1.html
🌀 The Van Allen Belts
In 1958, James Van Allen published data showing that radiation gets trapped in belts around Earth. These are now known as the Van Allen Belts. They’re zones filled with fast-moving protons and electrons that didn’t escape into space but got caught in Earth's magnetic field.
This is critical for satellite design: your spacecraft may be floating through these belts—getting hit by high-energy particles constantly. And here’s the tricky part: that radiation isn’t evenly distributed. Some regions are far more intense than others.
Credits: NASA
đź”— Want to understand why? I think this NASA resource is a great start: https://pwg.gsfc.nasa.gov/Education/wtrap1.html
⚙️ How Do We Quantify Radiation?
So far, we’ve talked about what radiation is. But how do we measure and model it?
In space, most radiation comes from:
Electrons and protons (trapped in belts or emitted during solar events)
Heavy ions (from supernovae or galactic cosmic rays)
Most of the radiation affecting satellites comes from the Sun. It’s the same solar activity that causes auroras. Importantly, the Sun follows an 11-year cycle—so the timing of your satellite launch matters.
Credits: NASA
Over the years, we’ve approached this problem empirically—by sending probes to space to measure radiation. These measurements led to models like:
AE-9 (trapped electrons)
AP-9 (trapped protons)
These help us estimate the kind of radiation environment a satellite will face.
Explore NASA’s mission here: 🔗 https://science.nasa.gov/mission/van-allen-probes/
🛠️ Let’s Try It Ourselves: Playing with OMERE
In the last post, I promised hands-on content. Let’s use OMERE, a tool that models space radiation environments.
Start OMERE and define your satellite’s orbit.
Go to Environment > Trapped Protons.
Click Calculate + Graph.
Trapped Particles Tab
You’ll now see plots showing the differential flux and integrated flux of particles:
Mean Spectrum of Trapped Particles
Differential flux = number of particles of a specific energy per cm² per second per MeV.
Integrated flux = number of particles above a certain energy threshold per cm² per second.
Want to explore more? Change the output to Spectrum along the orbit, and play with different options under Settings.
Trapped Proton Differential Spectrum Along the Orbit
🔍 Challenges and What's Next
By experimenting with different orbits and parameters in OMERE, you’ll notice some surprising trends. I’ll go deeper into those in upcoming posts.
In the meantime, I challenge you to play around with OMERE—change the orbit, vary the solar cycle, test different energy thresholds—and see how the radiation levels change.
See you in the next chapter!
