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The moon is the perfect place for SETI

In less than four years, NASA plans to land the first woman and next man on the moon as part of the Artemis project. This long-awaited return to the Moon must be followed by the construction of the Moon Gate, Artemis Base Camp and a program for “sustainable exploration of the Moon.” Creating a lasting human presence on the moon will also create many opportunities for exciting research.

For example, astronomers want to conduct radio astronomy in the far side of the moon, where telescopes can study the earliest period of the universe without terrestrial radio interference. Taking this step further, a team of astronomers recently recommended that the radio telescope on the far side of the moon (or in lunar orbit) help in another important area of ​​research: the search for extraterrestrial intelligence (SETI)!

The proposal was the subject of a white paper submitted to the Decade Survey of Planetary Science and Astrobiology of the National Academy of Sciences (NAS) 2023-2032. The team behind him was led by Eric J. Misho, a math student at UC Berkeley, and included members of the SETI Institute, the Institute of Space Science and Astronomy at the University of Malta, and Breakthrough Initiatives.

Illustration of the astronauts of Artemis on the moon. Credits: NASA

As they explained, the potential for lunar radio astronomy has been recognized since the days of the Apollo Program. Interest resumed in the early 2000s, at a time when the first steps were being taken to return astronauts to the moon (the Constellation Program). With the development of NASA’s plans over the last decade – the Moon to Mars and the Artemis Program – now is the time to make the necessary planning.

Dr. Pete Warden, chairman of the Breakthrough Foundation and former director of NASA’s Ames Research Center, co-authored the article. As he told Universe Today by email, the need to create space for such a telescope is imperative:

“There is a certain urgency in creating a lunar remote radio-quiet reserve before we get the growing problem we have in Earth’s orbit with optical interference from communications satellites. We are already concerned about Chinese communications satellites – so this must be a global consensus now! “

The benefits of lunar astronomy have been thoroughly studied. To begin with, the radio telescope on or in the moon’s orbit will allow highly sensitive radio astronomy experiments. On Earth, the most common radio frequencies used for communication are also considered profitable for SETI research. Unfortunately, their common use makes them subject to a great deal of interference.

Radio image of the night sky. Credit: MPIA / Glyn Haslam.

As such, Earth’s radio telescopes are based in parts of the world that have minimal “radio pollution”, such as deserts and remote areas. But the far side of the moon may be the most “quiet” place in the solar system. As Michaud explained to Universe Today by email, these benefits include the ability to scan:

“Frequencies dominated by [Radio Frequency Interference] RFI, as well as very low frequencies blocked by the ionosphere. Going into space solves the ionosphere problem, and going to the moon alleviates the RFI problem. “

As they point out in their study, radio noise can be particularly attenuated if a crater is chosen as the site for a surface observatory. Some sites of choice include the Sakha, Tsiolkovsky, Malapert and Daedalus craters, all of which have been selected as possible sites from previous lunar radio astronomy proposals. In such an environment, the walls of the crater would block interference coming from orbits or spacecraft.

Of course, the lunar surface telescope also has some drawbacks. For example, the observatory will require a mission to launch the ship to bring it to the surface, which is more complicated than sending missions into orbit. Here, Michaud and his colleagues use those of the Israeli Space Agency Beresheet and ISRO ‘s Vikram lunar landing (part of ISRO) Chandrayaan-2 mission) as examples, both crashed to the ground.

The Chinese landing Chang'e-4 on the lunar surface.  Image credit: CNSA / CLEP
The Chinese landing Chang’e-4 on the lunar surface. Credit: CNSA / CLEP

Another drawback is that the lander would not be able to draw solar energy during the 14-day lunar night, which means that it will have to come with a large battery. Communications would also be a challenge, as the far side of the moon is never in direct view of the Earth. Chinese Chang’e-4 the mission handles this by transmitting its communications to Queqiao an orbit that orbits the Moon at point L2 Earth-Moon.

On the other hand, a lunar telescope located in the Moon’s orbit would be cheaper to launch and could support a larger antenna – as the weightlessness of the orbit would eliminate the need for a supporting structure. But of course, such a mission has its drawbacks, such as the fact that RFI may be more of a problem from afar.

The nature of the Moon’s gravitational field also means that most lunar orbits are inherently unstable, leading to the decay of the orbit. Fortunately, Miko and colleagues point out that there are several “frozen orbits” where the orbit can remain stable for years. As Misho explains, a lot of work has to happen before the SETI lunar observatory can take place:

“The main weakness of the paper is that it is quite agnostic about what exactly the telescope should look like in the lunar orbit or on the lunar surface. I think the next step will be to develop some specific orbit projects. Some calculations also need to be made to determine the best orbit for such an instrument. “

Illustration of the artist for the new spacesuit created by NASA for the astronauts of Artemis. It is called xEMU, or Explore Extravehicular Mobility Unit. Credit: NASA

Dr. Warden, meanwhile, says NASA and the international astronomical community have got off to a great start. Project Artemis and Artemis Accords. They not only facilitate the return of the moon, but also create a framework for partnerships between nations and between the private and public sectors. This, explains Dr. Worden, will be essential for building the necessary infrastructure and support:

“This is an important science. I am convinced that we could start setting up these observatories on the lunar side, using systems like Blue Origin on Blue Origin to place a significant radio telescope on the far side by the middle of this decade. The cost of such a project would be comparable to large ground-based observatories, possibly in the hundreds of millions of dollars. This means that the system could be funded in part by private philanthropists, as are our main new ground-based observatories today. “

One of the most exciting things about the moon’s impending return is the types of science and additional missions it will allow. Once all the necessary infrastructure is built – the Lunar Gateway, Artemis Base Camp and others. – Astronauts will be able to perform surface missions with greater frequency and for longer periods of time.

In the long run, facilities could be built to allow lunar astronomy, lunar science and lunar tourism. The lessons learned from these endeavors may even open the door (dare we hope) to a permanent lunar settlement. Since all this will start in just a few years, the time to plan it is now!

Further reading: arXiv

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