M-42 EXT
DLR radiation dosimetry sensor aboard Orion offering six times the measurement resolution of its Artemis I predecessor.
Last refreshed: 6 April 2026
DLR's sensor is collecting the best-ever deep-space radiation data. Why is NASA keeping it private?
Latest on M-42 EXT
- How much radiation are the Artemis II astronauts being exposed to?
- DLR's M-42 EXT sensors are recording data continuously, but NASA published no public dose readings as the crew reached maximum distance on 6 April 2026, the mission's highest-radiation point.Source: Artemis II mission updates
- What radiation sensors does NASA use on the Orion spacecraft?
- Artemis II carries DLR's M-42 EXT dosimetry sensor, which provides six times the measurement resolution of the hardware flown on Artemis I.Source: DLR / NASA
Background
The M-42 EXT is a radiation dosimetry sensor built by DLR (German Aerospace Centre) and deployed aboard the Orion capsule for Artemis II. It delivers six times the measurement resolution of the dosimetry hardware flown on Artemis I, providing continuous crew radiation dose readings throughout the mission. As the crew reached maximum distance from Earth on 6 April 2026, the sensor was generating data at the mission's highest-radiation-exposure point.
Deep-space radiation is one of the primary physiological challenges of long-duration human spaceflight beyond Earth's magnetosphere. Unlike the ISS, which sits within the protective Van Allen belts, Orion transits an environment exposed to both galactic cosmic rays and solar energetic particle events. The M-42 EXT is designed to characterise that environment with higher fidelity than previous hardware, building the dose-response dataset needed for eventual lunar surface missions of days or weeks.
Despite continuous sensor operation, NASA published zero public radiation readings during the mission's maximum-distance phase. The data are being collected; the decision about what to release is a separate policy question. The M-42 EXT's improved resolution means any future disclosure will be significantly more informative than Artemis I data.