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Are aircraft crew and passengers exposed to increased radiation as they fly across the geographical region of the South Atlantic Anomaly (SAA)? Three researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) precisely measured the radiation levels experienced on board a non-stop flight from Hamburg to the Falkland Islands. Their first results are now available: at a cruising altitude of 43,000 feet (just over 13 kilometres), Earth's atmosphere still acts as an effective shield against cosmic radiation below the SAA.

The SAA is located off the coast of Brazil. It is caused by the shift of Earth's magnetic field axis, which does not pass directly through the Earth’s centre. As a result, the inner Van Allen radiation belt in the South Atlantic region extends down particularly close to Earth. This leads to increased radiation levels in near-Earth space – home to the International Space Station (ISS) – in the region. Life on Earth is generally protected from cosmic radiation by both its magnetic field and its atmosphere, but this protective effect decreases with increasing altitude.

Flight through the entire geographical region of the South Atlantic Anomaly

"No additional radiation exposure could be detected for commercial flights travelling through the geographical region of the South Atlantic Anomaly. This has been confirmed by our preliminary analyses," says Matthias M. Meier from the DLR Institute of Aerospace Medicine in Cologne. "At cruising altitudes up to 13 kilometres, the SAA has no impact on radiation exposure under stable space weather conditions." The DLR team was able to verify its own model calculations on board a Lufthansa Airbus A350-900 and add to findings from previous measurement flights. The passenger aircraft traversed the entire geographical region of the SAA at a constant altitude of approximately 13 kilometres. The measuring instruments had their own seats in row 15 of the aircraft. They were installed close to the centre of gravity of the Airbus to reduce the effects of turbulence as much as possible.

Solar wind influences radiation exposure

The results of the measurements are particularly significant due to the currently low influence of space weather generated by the Sun. At the moment, solar activity levels are very low – there are very few sunspots, for example. "Solar activity is the motor driving the solar wind, which has a significant impact on how many energetic particles from the galaxy reach Earth," explains Meier, who leads the institute's Radiation Protection in Aviation Group. On the one hand, this means that the impact of galactic cosmic radiation is comparatively intense at the moment. On the other hand, it means that space weather conditions are very stable, and Earth's magnetic field as well as the radiation belts are not being significantly influenced by the Sun.

The Radiation Measurement In Space (RAMIS) detector on the Eu:CROPIS satellite has been collecting corresponding data from space since December 2018. Using these data, it has been possible to clearly measure the increase in galactic cosmic rays during the period of reduced solar activity. The satellite's orbit takes it over almost the entirety of Earth's surface. This makes it possible to determine how the galactic cosmic radiation varies according to the satellite’s position in orbit and the shielding of Earth's magnetic field.

Lufthansa's Airbus underway on behalf of research

In addition to the DLR team, the Lufthansa flight from Hamburg to Mount Pleasant on 30 March 2021 carried 40 crew members for the research vessel Polarstern. The flight facilitated Polarstern's crew exchange and the return of a team from Neumayer Station III in Antarctica. On 3 April 2021, the Airbus aircraft flew back from the Falkland Islands and landed safely in Munich. Lufthansa’s first non-stop flight of this distance carried scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) at the end of January. The AWI operates the Polarstern and Neumayer Station. Before the flight, the research team and the Lufthansa crew spent two weeks in quarantine.

DLR scientist Mona C. Plettenberg reported on her experiences before and during the flight via Instagram (@germanaerospacecenter, Atlantic Kiss) and Twitter (@DLR_de).

Interview with Matthias M. Meier, head of the Radiation Protection in Aviation working group, after returning from the Falkland Islands.

What was the situation on board the aircraft?

We had instruments for recording different components of the radiation field, including a 40-kilogram neutron sensor in a specially padded case. We fixed the cases with the large measurement instruments to the seats so that the measurements would not be distorted by vibrations during turbulence. We then had a relatively quiet flight, which gave us excellent measurement results. We recorded the radiation exposure not only in the geographical region of the South Atlantic Anomaly, but also far beyond it, within the region between 50 degrees north and 50 degrees south – roughly the latitudes of Cologne and the Falkland Islands.

How long did it take to prepare for the campaign?

Our measurements were actually planned for June 2020. We would have used a scheduled flight from Frankfurt to Buenos Aires for this, but that was not possible due to the COVID-19 pandemic. Then, at very short notice, we were given the opportunity to fly on the Lufthansa Airbus that was to be flown on behalf of the Alfred Wegener Institute. This was a unique opportunity for us, as we reached a cruising altitude of 43,000 feet just past the equator.

What is the significance of the measurement results?

Until now, we had model calculations for a flight altitude of 13 kilometres, but no measurement data of our own. The predictions from our cosmic radiation model PANDOCA have now been entirely confirmed for this flight altitude too. Moreover, we were also able to collect extensive data on the radiation field at cruising altitudes, which we are now evaluating.