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Space Weather Clears for the Flyby Window

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12:59UTC

Region 4409, which fired 23 of 24 flares in a single day, went quiet on the one day it mattered most.

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ScienceDeveloping

Key takeaway

The sunspot region that threatened the flyby produced only minor flares on the day of maximum crew exposure.

NOAA's three-day forecast for 6 to 8 April showed a maximum Kp of 3.0, well below the G1 storm threshold.¹ SpaceWeather.com recorded only B9 and C2 class flares on 6 April, with a Kp index of 2.0 and all sunspot magnetic fields stable.² Solar wind speed sat at 539.4 km/sec with a northward Bz of 0.75 nT, conditions that reduce coupling to Earth's magnetic field.

The 20% daily X-class flare probability from Region 4409 that hung over the mission through update #4 did not materialise. The G3 geomagnetic storm that peaked at Kp=7 on Days 3 and 4 resolved four days ago. Two days ago Region 4409 produced an M7.5 , the strongest flare of the mission week. Today, with the crew at maximum distance and behind the Moon, it produced nothing above C2.

Region 4409 remains active; it previously fired 23 of 24 flares, or 96%, in a single day, including three M-class events.³ The same sunspot group that threatened the flyby went quiet on the one day it mattered most.

Deep Analysis

In plain English

The Sun is not constant. It has active regions, called sunspots, that can fire powerful bursts of radiation called solar flares. A strong enough flare, if it hits a spacecraft in deep space, can deliver a significant radiation dose to the crew. Region 4409 was a particularly active sunspot that had been firing flares throughout the mission. In the days before the flyby, forecasters gave it a 20% daily chance of firing an extreme X-class flare. On 4 April, it produced an M7.5 flare, one of the strongest during the mission week. On 6 April, the most important day of the mission, Region 4409 went quiet. Only minor B9 and C2 flares occurred. The space weather cleared exactly when it mattered most.

What could happen next?

Consequence
Quiet space weather on 6 April kept crew radiation dose within expected margins, though the exact figures remain undisclosed by NASA.

Sources:NASA·NASA·NOAA Space Weather Prediction Center

Mentions:G3 geomagnetic storm →NOAA →Region 4409 →Space weather →Space Weather Prediction Center →

First Reported In

Update #5 · Records fall while Orion goes silent

NASA· 6 Apr 2026

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Causes and effects

Caused by

G3 storm hits crew in deep space

The G3 storm peaked on Days 3-4 from a different solar event; Region 4409's quiet on 6 April contrasted with the prior storm severity, with the sun going calm on the mission's highest-risk day.

Occurred 4 Apr 2026

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This Event

Space Weather Clears for the Flyby Window

The 20% daily X-class flare probability that hung over the mission through previous updates did not materialise, leaving Kp=2 quiet conditions for the flyby.

Different Perspectives

JAXA

JAXA is an Artemis Accords signatory with the Lunar Cruiser rover planned for south-pole surface operations; Chang'e 7's first-arrival timeline compresses the window those surface systems were designed to operate in alongside American crew.

Space Research Institute RAS / Roscosmos

The LILEM instrument on Chang'e 7 gives Russia science-cooperation presence at Shackleton's rim with no independent crewed lunar capability on a public timeline. This is Roscosmos's only confirmed path to south-pole science in the current decade.

CNSA / China Manned Space Agency

Chang'e 7 at Wenchang confirmed a second-half 2026 launch for Shackleton rim, 18 to 24 months before any American crewed arrival. The mission carries a Russian LILEM instrument, giving Roscosmos a south-pole science foothold inside China's programme.

Jeremy Hansen / Canadian Space Agency

Hansen appeared at the 16 April JSC press conference in his only public moment since splashdown. Canada's Canadarm3 remains without a confirmed deployment host after Gateway cancellation, with CSA maintaining institutional silence on the programme's status.

Airbus Defence and Space

Airbus has issued no post-mission ESM performance statement; its press room returned a 404 error on a 14 April check. The only named Airbus engineer quote on the mission appeared in a Nature interview, not a company release.

Daniel Neuenschwander / European Space Agency

ESA's 11 April statement praised ESM translunar injection precision and omitted the pressurisation valve anomaly; the June 2026 Council is the sole stated review forum. ESM-3 is at KSC without a corrected-baseline disclosure to justify its readiness.