Why NASA’s Artemis lunar missions are a game changer for astronomy

As the U.S. government cuts spending on basic science, one thing seems certain: There’s still plenty of money left to return to the Moon.

NASA’s Artemis II mission is just the tip of the space agency’s lunar exploration spear: planning for a plethora of additional crewed and robotic follow-ups is well underway. And all these trips could also carry equipment for groundbreaking research.

There is a lot to learn about the Moon. Most of it is about the moon itself– its obscure origins, its long history and even vital resources it could hold. But some astronomers, confronted with more and more austere Government funding for their ground and space projects is beginning to view the Moon as a more financially stable scientific stop for some of their most ambitious cosmic studies.

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An antenna on the far side of the Moon

Anže Slosar, a physicist at Brookhaven National Laboratory, once hoped to install a radio telescope on the far side of the Moon, but abandoned his dream years ago. The mission simply seemed too expensive and didn’t generate enough interest. “After the Apollo landings, we thought, ‘We made it,’ and that was it,” he recalls.

Sentiments changed under the first Trump administration. One day, Slosar received an email from a Department of Energy program director asking if he still thought building a distant radio telescope was possible and if he was interested in leading the DOE’s involvement in such a project.

“This is an unusual path for science,” Slosar says. “Usually you have to jump through a lot of hoops, and now we just received funding for this project out of nowhere. »

It was the simplest choice of his professional career. “I said, ‘Of course!’ “, he remembers. “It changed my life forever.”

The reason for Slosar’s enthusiasm is that a radio telescope on the Moon could do things that none on Earth can do. Ground-based radio telescopes can only collect signals from a limited range of wavelengths. This is because when air molecules in the upper atmosphere absorb the sun’s ultraviolet rays, they become so excited that they lose their electrons and become “ionized” in the process. For most radio waves, the resulting ion-filled layer – the ionosphere – resembles a giant mirror, blocking many incoming cosmic messengers.

Unfortunately, the solution is not as simple as removing Earth’s atmosphere or, more likely, launching a radio telescope into space. To be of great use to radio astronomers, any space observatory would have to be extremely sensitive, so sensitive, in fact, that its observations would inevitably be overwhelmed by telecommunications emanating from Earth. To connect to distant galaxies and other distant objects, astronomers would need an antenna somewhere without an atmosphere, which would also be somehow shielded from all our earthly chatter.

Such a place exists, of course, and it is only a stone’s throw from our third rock from the sun. The Earth is locked in a synchronous dance with the Moon, so that the same lunar hemisphere always faces us. On this most distant surface, the Moon itself acts as a shield against the cacophony of Earth’s radio signals. This is exactly why Houston Ground Control lost contact with Artemis II for approximately 40 minutes while Lunar flyby on April 6, when the mission’s Orion spacecraft was obscured by the moon.

“Behind the Moon, at the right time, you can avoid interference from the Sun and Earth,” says Slosar. “This becomes one of the quietest places in our solar system to observe these radio frequencies.”

This expanse of wavelengths proves to be a window into the most mysterious era in the history of the universe.

Our oldest snapshot of the universe dates from around 380,000 years after the Big Bang. It is known as the cosmic microwave backgroundor CMB, and is made up of the light that was released when the hot, dense plasma that permeated the early universe cooled enough to form hydrogen atoms. Just like the swarms of radioblocking electrons in Earth’s ionosphere, unbound electrons in this ancient ionized plasma also blocked light. So when they all transformed into atomic hydrogen, the light that had spent millennia hidden by the primordial fog was released to flow freely throughout the universe. Today we see this “last broadcast surface” as a diffuse radio glow throughout the sky.

But for hundreds of millions of years after that singular moment, we have virtually no data. That’s because the universe was filled with relatively cold, light-choking hydrogen, which emitted virtually no light of its own. It wasn’t until stars and galaxies started forming from all that hydrogen that there was enough light and heat to reionize some hydrogen atoms, making these growing cosmic structures visible to our telescopes.

There was a little light in what we call cosmic dark ageshowever: a thin stream of radio emissions with a wavelength of 21 centimeters emanating from hydrogen atoms. Astronomers have managed to detect 21cm cosmic signals through heroic efforts using ground-based instruments, but the noisy and patchy picture painted by these detections is woefully incomplete. To map the dark ages in all their hidden majesty – to discover how, exactly, cold matter coalesced into luminous cosmic structures – the best option, by far, is to search on the other side of the moon.

This is where Slosar comes in. He now leads DOE’s contributions to its partnership with NASA on a project called Lunar Surface Electromagnetic Experiment-Night (LuSEE-Night), which aims to launch to the far side of the Moon in December 2026. He will fly aboard. a Blue Ghost lander from Firefly Aerospace within the framework of NASA Commercial Lunar Payload Services (CLPS) Initiativewhich relies on landers built and operated by private industry to transport spacecraft, experiments, and other payloads to the Moon’s surface.

Once there, LuSEE-Night’s biggest challenge will be navigating the cryogenically cold lunar night, which lasts the equivalent of about 14 Earth days. Pink Floyd may have misled you: the dark side of the moon is not always dark. But when it does, it’s an inhospitable place: few experiments survive the night.

Ultimately, the mission is meant to be a pathfinder, proof that even bigger and bigger radio telescopes can be built and operated on the far side of the Moon.

A gravitational troika

A free trip to the Moon would be a dream for the newcomer to the ranks of astronomers, passionate about gravitational waves.

It was just 11 years ago that science has acquired the ability to scan the sky for these elusive waves, thanks to the laser interferometer gravitational wave observatory. Better known as LIGO, this project uses, you guessed it, lasers to detect the subtle stretching of space and time resulting from the cataclysmic merger of two gigantic black holes.

The European Space Agency’s next project Laser Interferometer Space Antenna (LISA) Mission– essentially LIGO in space – will develop the revolution launched by LIGO. Launching as early as 2035, LISA could detect waves from much more massive mergers of supermassive black holes rather than waves from small black holes of stellar mass 50 that fall under LIGO’s purview. It will also detect the slower ripples of calmly orbiting binaries, emitted well before their death spiral begins. Both of these sources produce waves with millions of kilometers between peaks, too long for a land-based instrument to record.

But to complete their coverage of the gravitational wave spectrum, astronomers have their eyes on the Moon. THE Lunar Laser Interferometer Antenna (LILA) would bridge the gap between LIGO and LISA by tuning to waves of intermediate wavelengths. These would include those resulting from the merger of white dwarfs, the astronomical objects that produce many of the supernovae that we observe and study by analyzing their electromagnetic emissions. LILA would also capture gravitational waves from neutron stars and black holes just as they began their final descent toward coalescence, providing an early warning system that could alert LIGO of collisions two weeks before they occur.

“There is no other place in the solar system where we can detect gravitational views in this middle band,” says Karan Jani, an astrophysicist at Vanderbilt University and principal investigator of the LILA project. “There is only the moon.”

That’s because the Moon is much more geologically inert than our rowdy planet. “It doesn’t have as active a core,” Jani says, meaning the lunar surface can be a quiet platform for gravitational-wave detection laser systems tailor-made for the mid-band.

LILA will essentially be built from mirrors mounted on rovers. The project team hopes to participate in an upcoming CLPS mission. When the lander opens onto the lunar surface, two mirror-equipped rovers will head in different directions, forming a five-kilometer triangle with the lander as the third point of the triangle. Then, an instrument on the lander will send lasers toward the rovers to compare their distances with microscopic precision.

“To be honest, we wouldn’t think about LILA if the United States didn’t go to the Moon,” says Jani. The LILA team hopes to reach a later phase of the project that will run in collaboration with NASA’s Artemis program and rely on astronauts for operation and maintenance.

A stellar feat

Observatories such as the James Webb Space Telescope (JWST) and the Hubble Space Telescope (and, for that matter, your typical consumer reflector telescope) are all based on the same principle: a mirror curved in such a way as to channel incoming light from multiple directions onto a single focal plane. Large telescopes use segmented mirrors to collect more light from a distant object and produce a sharper image; The main mirror of JWST consists of 18.

Optical interferometry is a way to greatly enlarge the light-collecting surface of a telescope by spreading these segments over an even larger area. In this approach, individual mirrors are linked together in an array, with each node channeling its light to a central facility that carefully corrects and combines these inputs, forming a much more powerful telescope.

Building on the Artemis program, NASA scientist Kenneth Carpenter aims to build an optical interferometry facility on the Moon. This proposed Artemis Compatible Stellar Imager (AeSI) consists of 15 to 30 mirrors mounted on a rover, allowing reconfiguration and other fine-tuning on the fly so that the imager can fixate on any target in the lunar sky. In addition to being a powerful technology pioneer, AeSI could also monitor many stars across a significant portion of the Milky Way. By studying them in ultraviolet light that Earth-based observatories can’t access due to Earth’s UV-blocking ozone layer, the project could literally shed more light on the still-mysterious details of stellar activity across the galaxy.

“We have wonderfully high-resolution data on the sun,” says Carpenter. “But we still haven’t developed a good predictive model for future activity.” Scientists’ best solar models currently struggle to accurately predict the surges of our most familiar star. But the hoped-for vast stellar data sets that AeSI could provide could help change that.

The project could also benefit from astronautic interventions, Carpenter says, meaning maintaining AeSI could be another possible task for Artemis crews that NASA is considering. land on the moon by 2028 and throughout the 2030s. If his decades of experience working on the Hubble Space Telescope have taught him anything, it’s that troubleshooting an experiment is infinitely more effective with a human on site.

“The Space Shuttle and Hubble were designed with each other in mind,” he says, referring to the 1993 STS-61 mission, which included a spacewalk to solve a critical problem with Hubble’s mirror. This historic telescope, says Carpenter, “probably would have been a failure without the collaboration of the human spaceflight program.”