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Cislunar Communication: The Time for Resolution is Now

In our third blog on topics to be discussed at WRC this month, we’re looking at cislunar communication. A topic which has received very little attention until recently. That, however, is simply because it is only now, as technology and capabilities have advanced, that it is moving from the realm of the theoretical to the practical.

Currently, there are two mechanisms in place to protect and manage cislunar (also known as xGEO) communications: Article 22 of the ITU Radio Regulations, and guidelines issued by the Space Frequency Coordination Group (SFCG).

In 1971, the World Administrative Radio Conference, the forerunner of WRC, enshrined in Article 22 of the ITU Radio Regulations, protection of the shielded zone of the Moon (SZM) so that this area could be used for radio astronomy and other passive services. The SZM is essentially an area of the Moon’s surface and associated airspace that is shielded from any emissions originating within 100,000 kilometers of the earth’s center.

The SFCG is comprised of national and international space agencies invested in ensuring that spectrum resources are used judiciously for the benefit of humanity.

Unfortunately, neither of these have “teeth.” It is not currently a requirement for administrations to either describe or commit as to how they would protect radio astronomy observations specified in Article 22. Similarly, implementation of SFCG recommendations depends on voluntary acceptance by member agencies. SFCG recommendations are further weakened by the fact that some of the parties planning Moon missions are not eligible for membership and, in any case, the SFCG recommendations are non-binding for commercial companies.

Competing Interests

In 1971, the idea of putting radio telescopes on the Moon was a dream. Now, as astronomy from Earth is encountering increasing levels of interference and technology has advanced, that dream is taking shape, and several nations now have plans to locate telescopes there. Quite simply, the view of distant galaxies is better from space than from Earth, as the James Webb Space Telescope and its predecessors have proved.

This presents two issues. Firstly, one way or another, information gathered by these telescopes needs to be transmitted back to earth. Secondly, astronomers are not the only people eying up the Moon. Private companies and national space administrations are also planning Moon missions for a variety of purposes, including exploration, manufacturing, and mining. So, we are now at a point where there needs to be clear protection, definition, and assigned frequency allocations.

The race to the Moon and beyond is the new space race, with several countries, including the US, China, India, and Russia undertaking lunar missions. This means that it is now more important than ever that clear guidelines and regulations are established, as competing interests vie for access to lunar resources. While some of this is competitive, some is also cooperative. The Artemis Accords, instigated by NASA in conjunction with the US Department of State in 2020 and now signed by 32 nations, lay the groundwork for expeditions to the Moon and beyond for exploration and use of outer space. China and Russia are members of the International Lunar Research Station moonbase collaboration. An objective for both coalitions is to establish a sustainable and robust presence on the Moon by the next decade.

Artemis I, launched in November 2022, carried the Orion spacecraft to the Moon, where it orbited 130 kilometers above the lunar surface. Artemis II, planned for a 2024 launch, will take astronauts further into space than ever before, and Artemis III, planned for the following year, will land the first crew on the Moon since 1972. Artemis IV and V (planned for 2028 and 2029) will deliver and put into lunar orbit sections of a lunar gateway. Components for Artemis, including spacecraft, robotics, and lunar rovers will be supplied by a variety of governmental and private organizations from signatory nations.

While the Accords do not reference frequencies specifically, they call for partner nations to “utilize open international standards, develop new standards when necessary, and strive to support interoperability to the greatest extent practical.”

A second cooperative venture, the International Lunar Research Station Cooperation Organization (ILRSCO), led by China, has a similar objective to the Artemis Accords, namely to establish a sustainable and robust presence on the Moon by the next decade. Current signatories to the organization include Russia (a founding partner), South Africa, and Venezuela.

The Way forward

At WRC-23, Agenda Item (AI) 9.2 asks the Conference to consider whether the Radio Regulations should be amended to require that any new lunar filing submissions commit to and/or demonstrate how they could meet the requirements of Article 22. This would protect the SZM and, obviously, please astronomers. Commenting on this, Alexandre Vallet, Head of Space Services at the ITU, said, “In my view, they will succeed in keeping it (SZM) quiet.”

Separately, under AI 10 there is an Inter-American Proposal to consider frequency allocations and/or identifications for lunar surface communications. This proposal specifically identifies cellular frequencies developed by 3GPP as potentially suitable for use by user groups spread over a wide area with high data throughput requirements. This AI proposes studying these frequencies to see if they meet the criteria for shared communication systems on the Moon. Frequencies of interest are: 390-450 MHz, 2 400-2 700MHz, 3 500-3 800 MHz, 5 150-5 925 MHz, and 25.25-28.35 GHz. It also proposes the development of a new regulatory framework.

Given the acceleration of interest in lunar exploration and development, the current situation is untenable. A free-for-all is not the way forward when it comes to frequency usage, making these AIs particularly important and ones to watch.

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