A 4G network on the moon is bad news for the radio …

As you drive down the road to the Jodrell Bank Observatory, a sign will instruct visitors to turn off their cell phones. The Lovell telescope is so powerful that it can detect a telephone signal on Mars.

Radio telescopes are incredibly sensitive. To quote the legendary astronomer Carl Sagan: “The total amount of energy from outside the solar system that has ever been received by all radio telescopes on planet Earth is less than the energy of a single snowflake hitting the ground.”

The total energy is probably worth a few snowflakes by now, but it is still true that astronomical radio signals are typically smaller than artificial ones. If Jodrell Bank could sense interference from a telephone signal on Mars, how would it fare with an entire 4G network on the moon?

This is the problem that worries astronomers like myself after Nokia of America received $ 14.1 million ($ 19.8 million) to develop the first cellular network on the moon. The LTE / 4G network is designed to facilitate the long-term habitability of the moon and enable communication for key aspects such as lunar rover and navigation.

Network outages

Radio frequency interference (RFI) is the long-term nemesis of radio astronomers. Jodrell Bank, the world’s first surviving radio astronomy observatory, was founded as a result of RFI. One of the pioneers of radio astronomy, Sir Bernard Lovell, discovered that his work in Manchester was hampered by radio interference from passing trams around the city and convinced the university’s botany department to let him move to their fields in Cheshire for two weeks (not I leave her)).

Since then, radio telescopes have been built further and further away to avoid radio interference. The next Square Kilometer Array (SKA) telescope is under construction in remote areas of South Africa and Australia. This helps eliminate many common sources of radio interference, including cell phones and microwave ovens. However, terrestrial radio telescopes cannot completely avoid space radio sources such as satellites or a future lunar telecommunications network.

RFI can be reduced to the source through adequate shielding and precision in signal output. Astronomers are constantly developing strategies to remove RFI from their data. However, this increasingly relies on the goodwill of private companies to ensure that at least some radio frequencies are protected for astronomy.

A long-term dream of many radio astronomers would be to have a radio telescope on the other side of the moon. Not only is it protected from terrestrial signals, it can also observe at lower radio frequencies, which on Earth are particularly affected by a part of the atmosphere known as the ionosphere. Observation at low radio frequencies can help answer fundamental questions about the universe as it was in the first moments after the Big Bang.

The scientific case has already been identified with the Netherlands-China low-frequency explorer, a telescope repurposed by the Queqiao satellite that was sent to the moon on the Chang’e 4 mission. NASA has also funded a project on the feasibility of transforming a lunar crater in a radio telescope with wire mesh coating.

It’s not just 4G

Despite its interest in these radio projects, NASA also has commercial partnerships. Nokia is just one of 14 American companies NASA is working with in a series of new partnerships worth more than $ 370 million ($ 519 million) to develop its Artemis program, which astronauts will work with until 2024 Moon is expected to return. .

The involvement of private companies in space technology is not new. And right and wrong have long been debated. Arguably the biggest eye-catcher are SpaceX’s Starlink satellites, which caused a sensation among astronomers after their first major launch in 2019.

The images quickly emerged with traces from Starlink satellites obscuring or clouding the original astronomical targets.

Astronomers have long had to contend with satellites, but Starlink’s number and brightness are unprecedented and their orbits difficult to predict. These concerns apply to anyone who practices terrestrial astronomy, whether using an optical telescope or radio telescope.

The SKA organization recently published an analysis of the impact of satellites on radio astronomy, which is developing the next generation of radio telescope technology for the square kilometer array. It has been calculated that SKA telescopes are 70% less sensitive in the radio band used by Starlink for communication, provided that 6,400 Starlink satellites are eventually deployed.

As space becomes more commercial, the sky is filling with increasing technological volume. That is why it has never been more important to have regulations to protect astronomy. To ensure that as we move further into space, we can continue to see it from our home on earth.

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Emma Alexander, PhD student in astrophysics, Manchester University

This article was republished by The Conversation under a Creative Commons license. Read the original article.