Lessons from an SOS signal on space weather

Juanma Gallego

The beginnings of the 20th century were epic times. On our planet there were still unexplored places and environments and expeditions to discover those unique sites were happening. At that time the first steps in aviation had begun to be taken and wireless communications were in a similar situation. At times when all these milestones converged, very curious stories occurred. One of these stories was the expedition of the airship Italy to the North Pole.

On May 25, 1928 Italy returned to its base after flying over the North Pole when it was shipwrecked about 400 km northeast of the Svalbard Islands (Arctic ocean). The survivors tried unsuccessfully to send distress messages through a portable high frequency (HF) radio transmitter, to establish a radio link with the Italian navy ship Città di Milano, anchored in the archipelago Svalbard.

A team made up of members of the Istituto Nazionale di Geofisica e Vulcanologia of Italy ( INGV ) and the Rutherford Appleton Laboratory of the United Kingdom ( RAL ), has analyzed since the perspective of space weather what happened in the emission of said SOS signals. The results indicate that the spatial weather conditions of the time had a significant influence on the dispatch of SOS. Researchers have pointed out that a lot can be learned from this type of event and they hope it can help prevent something similar from happening in space exploration.

On April 15, 1928, the airship Italia took off from Milan with the hope of being the second aircraft to reach the North Pole (two years earlier the airship Norge had succeeded). On May 24 the expedition achieved its objective. Exulting with joy, they were about to get off the ship to step on the snow, but did not do so because they had a worrying-looking polar storm above them. The return, however, turned into a nightmare. The Italy collapsed and the strong winds carried away the airship. 17 members of the expedition lost their lives dramatically.

The nine members of the crew who were in the main basket had better luck and, although many of them were injured, they managed to survive on an ice sheet, about 400 miles from the Svalbard Islands. Some instruments were not damaged in the accident, they could be used, and among them was a radiotelegraph. They had a way of saving themselves, or so it seemed.

However, sometimes fate turns out to be very capricious. They issued messages asking for help. Despite trying over and over again on different frequencies, his messages were getting no response. That didn't make sense. They listened to the radio: they were able to listen to a radio station in Rome, 4,000 kilometers away, and also the messages sent by the ship Città di Milano . This ship was a support ship for the expedition, but they did not receive the messages requesting help from the expedition members. Faced with this supposed silence, the world declared all the explorers missing.

Ten days later, when all seemed lost, a Russian radio amateur received an SOS signal from the survivors. Rescue work was not easy and they had to spend weeks on a drift ice sheet. But that's another story.

An article published in the magazine Space Weather has tried to clarify what happened on that expedition. And, yes, as can be deduced from the name of the magazine, space weather had a lot to do with it. Experts who have analyzed the issue assure that the castaways were exposed to a radiophonic vacuum or silent zone, a region where a radio transmission cannot be received. In this region, no signal can be picked up because, due to local ionosphere conditions, radio waves are not reflected but rather penetrate the ionosphere. The exact location of this void can vary according to ionosphere conditions, and researchers believe that was what happened in 1928.

We must bear in mind that radio communications use the ionosphere – located at an altitude of between 50 and 1,000 kilometers – to spread over great distances. Basically, radio waves are reflected off that layer and bounced back to the ground, making transmission possible. But near the poles, that layer, which is normally quite stable, becomes more unstable.

The authors of the study believe that various phenomena associated with solar storms converged at that time. Although today we know that this type of phenomenon occurs, at the time of Italy they were unaware that solar storms affected radio emissions. They knew that the weather in the vicinity of the North Pole was extreme, but they could not even imagine that in that area something called space weather would have to be taken into account.

The portable radio available to the castaways it emitted at frequencies from 9.1 to 9.4 megahertz, but in the Svalbardas there was the phenomenon of radio vacuum mentioned above for that frequency section, and it was in that area where the support ship was located. On the other hand, a solar storm worsened the situation, increasing the absorption of radio waves. For this reason, the authors believe that at least in the first days the range of usable frequencies decreased greatly.

To reconstruct the situation of the ionosphere in those days, historical data collected in several observatories have been used: the Abinger observatory in the United Kingdom (today known as Hartland ), that of Lerwick and the Royal Observatory of Belgium .

In statements to the magazine OSE of the American Geophysical Union, Ljiljana Cander, physicist and co-author of the study, has emphasized that «this is a history lesson that could be reproduced during other explorations such as lunar or interplanetary travel, so they should be taken into account even more possible communication problems due to adverse spatial climatic conditions. ”

Researchers have highlighted that the study of past events can be a useful and valuable source of information in the field of space meteorology, a still relatively young discipline. In this sense, we must remember, for example, how important it is to analyze the Carrington event the largest known solar storm since there are reliable historical records.

Bibliographic references:

Zolesi, B., Pezzopane, M., Bianchi, C., Meloni, A., Cander, LR, & Tozzi, R. (2020). The shipwreck of the airship "Dirigibile Italia" in the 1928 polar venture: A retrospective analysis of the ionospheric and geomagnetic conditions. Space Weather 18 (7), e2020SW002459. DOI: https://doi.org/ 10.1029 / 2020SW002459

About the author: Juanma Gallego ( @juanmagallego ) is a science journalist. [19659003] This article was originally published in Euskara on July 17, 2020 on the blog Zientzia Kaiera . Article original .

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