From RAM to CAD: The Evolution of Astronaut Radiation Monitoring Through Artemis II

NASA’s Artemis II mission returned to Earth on April 10, 2026, marking humanity’s first crewed journey around the Moon in more than 50 years. During the mission each astronaut carried a small but critical piece of technology: a Crew Active Dosimeter (CAD) developed by Mirion in collaboration with the Space Radiation Analysis Group at NASA’s Johnson Space Center.

Worn in the astronauts’ pockets, these devices collected something mission planners have never had access to at this level of detail before: continuous, real-time insight into the crew’s individual radiation exposure throughout the journey from Earth’s orbit to deep space and back.

Beyond Apollo-Era Measurement

Radiation has long been one of the greatest unknowns and risks of human spaceflight beyond low Earth orbit. Earlier missions relied on Radiation Area Monitor (RAM) passive dosimeters for individual radiation monitoring, which provided valuable data but as a cumulative exposure over the entire mission. They also required post-mission processing and readout as well as a complicated logistics and analysis chain for their readout.

Mirion Crew Active Dosimeter is carried in astronauts’ pockets, collecting continuous, real-time measurements of radiation exposure. Actual flight units are pictured. Credit: NASA

The shift from RAM to CAD represents a fundamental change in how radiation is understood in space. Rather than capturing a single dose for an entire mission, available after the fact, CAD delivers time-resolved data. It provides a continuous stream of information showing how radiation levels fluctuate based on spacecraft position, shielding and space weather conditions.

This distinction is critical. On a mission like Artemis II, where astronauts travel beyond the protective magnetosphere of Earth, radiation exposure is not static. CAD allows NASA to observe those variations as they occur, creating a far more complete picture of the environment astronauts experience.

Instadose Technology, Reimagined for Deep Space

At the core of CAD is Mirion’s Instadose^® wireless dosimetry technology, widely used in medical and occupational settings on Earth and adapted for the extreme conditions of space.

Wireless dosimetry technology developed by Mirion Dosimetry Services for use in clinical and occupational settings was adapted to meet the rigors of space travel.

What sets this technology apart is the shift from passive measurement to active, on-demand monitoring.

With CAD, astronauts and mission control are no longer waiting to analyze exposure after the mission. Instead, they can access immediate data to understand the individual exposure of crew members to help inform operational decisions in real time, including responding to solar events.

Understanding the Space Radiation Environment in Real Time

CAD also enables more precise differentiation between radiation sources, including galactic cosmic rays and localized phenomena such as transits of the Van Allen belts or solar particle events.

For Artemis II, this means the mission not only measured radiation but also is refining the models that will guide future crewed missions to the Moon, Mars and beyond.

Why This Matters for the Future of Human Spaceflight

Artemis II served as a proving ground for the technologies that will support long-duration exploration missions.

Radiation remains a key constraint on how far and how long humans can travel in space. By delivering real-time, individualized exposure data, CAD helps turn radiation from an uncertain hazard into a measurable and manageable risk.

The impact extends beyond space. The same underlying technology has already influenced radiation monitoring in healthcare and other industries, demonstrating how innovations developed for space exploration can benefit life on Earth.

“Technology we’ve developed to meet the demands of spaceflight often informs how we approach radiation safety and measurement across other applications such as healthcare, environmental testing and research on Earth,” said Thomas Logan, Mirion Chairman and Chief Executive Officer. “The CAD is a powerful example of how collaboration in space exploration technology can drive broader advances in radiation safety.”

A Small Device with Mission-Critical Impact

Artemis II has concluded its journey, and the CADs worn by the crew returned with more than just data. They are delivering insight into how radiation behaves in deep space, how humans interact with that environment, and how future missions can be designed more safely.

In the effort to return humans to the Moon and eventually send them to Mars, it is often the smallest technologies that make the biggest difference.

Learn more about how Mirion technology supports space exploration here.

References

• ScienceDirect, “The Importance of Time-Resolved Personal Dosimetry in Space: The ISS Crew Active Dosimeter,” https://www.sciencedirect.com/science/article/pii/S2214552423000627#sec0016 
• NASA, “Why Space Radiation Matters,” https://www.nasa.gov/missions/analog-field-testing/why-space-radiation-matters/