Protecting Artemis and lunar explorers from space radiation

The Artemis I mission, which is scheduled to launch on August 29, will be a key step toward humankind's return to the moon. While no humans are on board this test flight, future missions will take space explorers beyond the protective confines of Earth's atmosphere and magnetic field and into the region of unrestricted space radiation. While solar flares and small to medium-sized coronal mass ejections are spectacular, they are unlikely to pose a significant risk to Artemis I or future crewed lunar missions.

Solar energetic particle events" should be avoided. They arise when particles released by the sun, primarily protons but also certain ionized atoms such as Helium, are propelled to near relativistic speeds. These high-energy particles fired across space can have an impact on a spaceship and its crew. Solar particle events are commonly connected with large solar flares and coronal mass ejections, as these eruptions may generate shockwaves that propel solar particles to deadly speeds.

When it comes to the Artemis missions, the walls of the space capsule Orion and its European Service Module were built to maintain the dependability of critical systems during radiation events, so much of the radiation from a particle event would be shielded. However, the event might disrupt communications between the crew and teams on Earth, forcing the astronauts to take shelter in an improvised storm bunker, as happened on the Space Station in September 2017. Nonetheless, the Space Station was still safely within the safety of Earth's "magnetosphere," a magnetic field-protecting bubble that the moon lacks.

According to Melanie Heil, Segment Coordinator of the European Space Agency's Space Weather Office, leaving the magnetosphere is analogous to leaving a safe port and going out into the wild ocean. Radiation exposure for astronauts on the moon can be an order of magnitude more than radiation exposure on the space station and many orders of magnitude greater than radiation exposure on Earth's surface. Future astronauts will face greater hazards from solar particle events; thus, it is critical that we investigate the radiation environment beyond the magnetosphere and increase our capacity to anticipate and prepare for solar storms.

A series of intense solar storms, including substantial solar particle occurrences, caused extensive interruption to satellites and ground-based communications systems on Earth exactly 50 years ago in August 1972. The storms struck right in the middle of NASA's Apollo 16 and Apollo 17 lunar flights, with just a few months between them. Fortunately, no human explorers were present beyond the Earth's protective magnetic field at the time. It is believed that if they had met similar storms from within the command module, the radiation dosage given would have resulted in acute radiation sickness. It might be fatal for an astronaut on a spacewalk.

According to Juha-Pekka Luntama, ESA's Head of Space Weather, reliable space weather services are required for lunar exploration and long-term settlement. A 1972-level catastrophe will occur again, and if we are not careful, astronauts will be in space and outside the safety of Earth's magnetic field when it occurs.

Until far, we've largely focused on the effects of space weather on Earth's infrastructure, such as power grids, communication systems, Earth-orbiting satellites, and astronauts on the International Space Station. The European Space Agency's Space Weather Service Network is dispersed across Europe, with professionals processing data from a variety of radiation detectors aboard satellites in space and sensors on Earth. They use this to deliver information and services to a wide range of "users," including satellite, airline, and power grid operators, as well as aurora seekers. During the Artemis I flight, the Network will continue to offer its services and will report any important space weather occurrence, whether forecast or imminent. However, for long-term human activities on the moon, we must directly monitor the lunar radiation environment.

The Artemis I test flight will be heavily focused on radiation research. NASA and ESA radiation sensors, as well as mannequins and CubeSats, will be aboard the Orion capsule to assist us better understand the radiation environment on the trip to the moon and its influence on human health. ESA is also working on the European Radiation Sensor Array (ERSA) project, which involves developing a set of instruments that will offer real-time radiation monitoring on the eventual crewed lunar Gateway space station.

Combining radiation measurements from the outside and inside of crewed habitats would allow researchers to monitor how much radiation "leaks" in and more precisely anticipate the risk to humans on the moon in the case of a space weather event. ESA researchers are also investigating the inclusion of radiation equipment on other unmanned moon orbiters, such as Lunar Pathfinder and future lunar telecommunication satellite networks.

Our star can be temperamental, but when 'active zones' arise on the solar surface, they tend to stay there for few days to several weeks. We could enhance our forecasts for space weather around Earth and the moon if we could monitor these areas even before they spin into view of Earth. One of the primary tasks of ESA's forthcoming Vigil mission is to observe active areas on the solar disk from which flares and mass ejections originate. Vigil, which is scheduled to launch in 2029, will go to the 5th Lagrangian point (L5), a unique position in orbit that will allow it to glimpse the sun's "side" before it turns into view from Earth.

Advance warnings for potentially dangerous space weather phenomena are predicted to be possible with Vigil several days before they threaten the health of people in orbit or infrastructure on and around Earth. This would be especially valuable for fragile lunar explorers and those planning high-risk operations like EVAs.

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