NASA’s Artemis II crew, NASA astronauts Reid Wiseman, commander; Victor Glover, pilot; Christina Koch, mission specialist; and CSA (Canadian Space Agency) astronaut Jeremy Hansen, shared brief remarks with friends, family, and colleagues after they landed at Ellington Airport near NASA’s Johnson Space Center in Houston on Saturday, April 11, 2026, after a nearly 10-day journey around the Moon and back to Earth. [Credit: NASA/Helen Arase Vargas]
NASA’s Artemis II astronauts safely returned to Earth on April 10 after completing a 10-day journey beyond our planet's protective magnetic shield. The trip spanned roughly 685,000 miles, marking the first crewed mission around the moon in more than five decades. While the world watched the launch and splashdown, NOAA space weather forecasters were watching something else: the sun.
Monitoring the Solar Environment in Real Time
Throughout the Artemis II mission, forecasters at NOAA’s Space Weather Prediction Center (SWPC) continuously monitored the sun for solar flares, coronal mass ejections, and high-energy particles that could pose radiation risks to astronauts traveling beyond the Earth’s protective magnetic shield, called the magnetosphere.
Illustration of Earth’s magnetosphere deflecting solar wind and energetic particles. During Artemis II, astronauts traveled beyond this protective boundary, where NOAA space weather observations and forecasts help assess radiation risk. [Credit: NOAA]
These observations were collected from NOAA satellites in geostationary orbit, instruments positioned at Lagrange point 1 (approximately one million miles from Earth), and additional data from partner missions. Together, those spacecraft provide continuous measurements of solar radiation, solar wind conditions, and particle energy levels.
How Warnings Reach the Crew
Space weather support for Artemis II followed a clear operational process. NOAA satellites collect observations of the sun and near-Earth space. Forecasters at NOAA’s Space Weather Prediction Center analyze that data and when certain thresholds are met, they will issue forecasts and official warnings if necessary.
During the mission, SWPC maintained an active operational posture. From launch through the end of the mission, forecasters issued more than 40 watches, warnings, and alerts, with heightened activity in the early days due to coronal mass ejections, geomagnetic storms, solar flares, and high-speed solar wind streams. In addition to routine forecasting, SWPC provided direct mission support, including coordination with the launch weather officer ahead of liftoff when there were concerns about potential increases in solar energetic protons. Those thresholds were ultimately not reached. Forecasters also delivered real-time decision support on-site to NASA teams in Houston on multiple occasions in response to evolving solar activity.
Those alerts are sent directly to NASA’s Space Radiation Analysis Group (SRAG), which evaluates radiation exposure risks using their operational procedures. If particle energy levels rise, especially solar energetic particles at or above approximately 100 megaelectron volts (MeV), SRAG assesses whether protective action is needed. If necessary, astronauts may be instructed to move to a more shielded area within the Orion capsule until radiation levels decrease. An electron volt represents a measure of energy and an MeV means one million electron volts.
During the Artemis II mission, solar activity remained within expected levels. No major solar radiation storms occurred, though monitoring continued around the clock to detect any potential changes.
“Space weather monitoring does not stop at Earth’s atmosphere,” said Yari Collado-Vega, the Project Scientist for NOAA’s Space weather Observations at L1 for Advanced Readiness (SOLAR) project and former director of the NASA Moon to Mars (M2M) Space Weather Analysis Office. “Our observations and forecasts give mission planners advance notice of solar activity so they can assess radiation exposure and take protective action if necessary.”
Crewed vs. Uncrewed Missions
Although the same space weather forecasts support both crewed and uncrewed missions, the stakes differ. High-energy particle events can damage spacecraft systems and onboard electronics, but for crewed missions, radiation exposure becomes a critical health concern.
Artemis II marks the first time since the Apollo era that astronauts have traveled beyond the protective shield of Earth’s magnetosphere, making real-time radiation monitoring especially important.
Lessons from the Apollo Era
Between the Apollo 16 and Apollo 17 missions, a significant solar energetic particle event occurred shortly after astronauts had completed spacewalks on the moon’s surface. At the time, forecasting capabilities were limited, and the crews were fortunate not to have been exposed during peak radiation conditions.
Today, advances in space weather monitoring and forecasting provide much greater coverage and accuracy, reducing uncertainty and improving mission safety.
As Missions Move Farther from Earth
Artemis II took place during an active phase of the sun’s 11-year cycle, when solar storms are more likely to occur and risks of radiation exposure increase once an object ventures beyond Earth’s protective magnetic shield.
As NASA prepares for future Artemis missions and eventual human exploration into deeper space beyond the moon, reliable space weather services will remain essential.
“Just as NOAA warns people about extreme weather to keep communities safe, NOAA provides space weather forecasts to protect society, critical infrastructure, and space exploration,” said Greg Marlow, director of NOAA’s Space Weather Observations Office. “As missions venture farther from Earth, timely solar observations and accurate forecasts become even more important.”