NASA’s mission to provide X-ray images of Earth’s magnetosphere

As part of the Artemis programme

NASA is set to provide the first-ever global images of Earth’s magnetic field, thanks to an innovative X-ray imager called LEXI (Lunar Environment Heliospheric X-ray Imager). As part of the US space agency’s Artemis programme, the state-of-the-art instrument is heading to the Moon, where it will provide critical insights into the magnetosphere that shields our planet from harmful solar radiation.

LEXI, one of ten payloads being delivered to the Moon through NASA’s Commercial Lunar Payload Services (CLPS), is scheduled for launch from Kennedy Space Centre, Florida, no earlier than mid-January 2025. It will travel aboard Firefly Aerospace’s Blue Ghost Lander, marking a pivotal step in NASA’s ongoing efforts to understand how space weather affects our planet.

Once it lands on the lunar surface, LEXI will power up and begin its mission of observing Earth from an unprecedented perspective. For six days, it will collect X-ray images emanating from the edges of Earth’s magnetosphere—the protective bubble that deflects the harmful solar wind. These X-rays are generated when charged particles from the Sun collide with the magnetosphere, a process that occurs at the magnetopause, the outermost layer of the magnetosphere.

A world-first

The significance of this mission lies in LEXI’s ability to capture a comprehensive, global view of these phenomena, something no other instrument has done before. While other satellites have detected these X-rays in isolated patches, LEXI will be the first to observe the full magnetopause from the vantage point of the Moon, offering an expansive view of this critical part of Earth’s space environment.

LEXI’s principal investigator, Brian Walsh, a space physicist at Boston University, says that the mission will allow scientists to study how the magnetosphere reacts to the changing forces of space weather.

“We’re trying to get this big picture of Earth’s space environment,” Walsh said. “This will be science that you can see,” highlighting the visual nature of the data LEXI will provide.

The instrument will track how the magnetosphere expands and contracts in response to variations in the solar wind. When the solar wind is strong, the magnetosphere contracts towards Earth; when the wind weakens, it expands. These dynamic changes, known as the magnetosphere “breathing,” will be observed for the first time globally.

In addition to mapping the magnetosphere’s movements, LEXI will also observe a phenomenon known as magnetic reconnection. This occurs when Earth’s magnetic field lines merge with those from the solar wind, releasing energetic particles that often spiral down towards the poles, creating brilliant auroras. However, these energetic particles can also pose a risk to infrastructure in space and on Earth, such as satellites and power grids.

Hyunju Connor, an astrophysicist at NASA’s Goddard Space Flight Centre and LEXI’s NASA lead, noted that understanding magnetic reconnection is key to predicting space weather events. “By understanding how nature behaves, we can help protect our infrastructure in space,” Connor stated, emphasising the importance of the data LEXI will provide for future space missions and Earth-based operations.

Interestingly, LEXI’s trip to the Moon will not be its first journey into space. In 2012, it was initially built as a prototype for a sounding rocket under the name STORM (Suborbital Test for X-ray Observation of the Magnetosphere). The instrument collected X-ray images before falling back to Earth.

After sitting for nearly a decade in a display case at NASA’s Goddard Space Flight Centre, the team decided to refurbish it for its new mission. Some components, including optics, were replaced, but the instrument was in good condition and ready to contribute to NASA’s lunar exploration efforts.

This repurposed technology, now rebranded as LEXI, is poised to deliver valuable data from the Moon’s surface.

Image: A rendering of the LEXI instrument onboard Firefly Aerospace’s Blue Ghost Mission 1, delivering 10 Commercial Lunar Payload Services payloads to the Moon. Credit: Firefly Aerospace/NASA