For the first time ever, a very low frequency radio telescope has successfully sent back astronomical data from the lunar surface. Although the mission didn’t quite go as planned, the data has enabled ground-based researchers to confirm the low frequency signature of our own Milky Way Galaxy. A team led by the University of Colorado at Boulder has published their results in The Astrophysical Journal.
We have demonstrated that radio astronomy from the Moon can be done at reasonable costs, and the science potential is high, Jack Burns, a co-author on the paper and a professor emeritus of Astrophysics at the University of Colorado Boulder, tells me via email.
The team used the NASA-funded $2.5 million ROLSES-1 (Radiowave Observations on the Lunar Surface of the photo-Electron Sheath) instrument sent to the Moon as part of Intuitive Machine’s 2024 Odysseus lander. Although Odysseus landed near the ‘Malapert A’ crater, within some 10 degrees of the Moon’s South Pole, it landed badly.
Even so, we managed to collect some data from the lunar surface that gave us a modest detection of our galaxy in the radio spectrum, Joshua Hibbard, the paper’s lead author and a doctoral candidate in astrophysics at the University of Colorado Boulder, tells me via email. The instrument was able to make the detection because the galaxy is extraordinarily bright at low radio frequencies, he says. That’s due to high energy particles spiraling in the galactic magnetic field and emitting enormous amounts of radiation, Hibbard says.
The spacecraft’s communications antennas ended up badly aligned and deployed horizontal to the lunar surface.
The lander came in “hot” with both vertical (6 mph) and horizontal (2 mph) velocities higher than expected, Burns tells me. The strut on one of the six landing legs absorbed the brunt of the lander impact, breaking its leg and causing the lander to tilt some 30 degrees to one side, he says.
The Good News?
We took data for about 80 minutes while in transit to the Moon with one antenna, says Burns. Then after landing, we deployed the remaining three antennas and over two days took about 20 minutes of data, he says.
As a result, the team was able to detect radio emissions from the Milky Way.
The disk and the halo of the Milky Way are chock full of high energy charged particles (cosmic rays) and magnetic fields embedded within the thin interstellar medium, explains Burns. And as high energy cosmic ray electrons spiral in the galaxy’s magnetic field, they decelerate and emit radio waves via a process called synchrotron radiation, he says.
And for the first time, the team detected this galactic synchrotron emission from the moon.
But is it really necessary to go to the Moon for radioastronomy?
Ground-based radiotelescopes all operate at higher frequences, says Burns. On the Moon, especially the far side, we operate at frequencies of tens of kHz to 50 MHz that are not accessible from Earth, he says. That’s due to radio frequency interference and because Earth’s ionosphere both refracts and absorbs radio emission, says Burns.
A Radio Noisy Earth Environment
The advent of numerous satellites orbiting the Earth makes radio astronomy more and more difficult these days, says Hibbard. So, there are many frequencies in radio astronomy that are now completely useless for science, he says.
But the lunar far side is the most radio quiet spot in the inner solar system. And because it always faces away from Earth, it is shielded from our planet’s natural and artificial radiomagnetic noise.
Yet why have Moon-based radio observations taken so long?
Lunar radiotelescopes have been proposed for the last four decades now. It’s a scientific tragedy that in the 50 years since NASA’s Apollo program went silent that it’s taken so long to utilize the perfect spot for low frequency radio observations from the lunar far side.
After Apollo was terminated by President Richard Nixon, we lacked access to the Moon, says Burns. Now, after half a century of technological advances, individual companies can design and build uncrewed spacecraft with NASA serving as the anchor client for space science payloads, he says.
What’s Next?
LuSEE-Night, the Lunar Surface Electromagnetics Experiment-Night, will launch in early 2026 to the Moon’s far side to do the first cosmological observations of the Dark Ages of the early Universe. And in 2028, ROLSES-2 will land on the lunar near side to complete science investigations originally scheduled for ROLSES-1.
And further down the road?
The NASA Innovative Advanced Concepts (NIAC) program has funded us to design the ultimate cosmology telescope on the lunar far side, called FarView, says Burns. It consists of 100,000 dipole radio antennas, he says.
The idea is to extract aluminum from the lunar regolith, in partnership with Lunar Resources, Inc. in Houston, using an electrolysis process that will enable the construction of the array’s dipole antennas.
This saves tons of mass that would otherwise be transported to the Moon at high expense, says Burns. We will be able to demonstrate advanced manufacturing and operate the first distributed scientific facility on the Moon, he says. We currently are in Phase II of funding from NIAC and we plan to propose for a Phase III study and to build a prototype array on the Moon, he notes.
Burns says the FarView project has targeted about a dozen potential far side sites for the observatory. And that he is meeting with NASA later next month to discuss a potential prototype for the mission.
A Unique Radio Probe Of Habitable Planets
Low frequency radio observations from the lunar far side can also uniquely probe and detect magnetic fields associated with potentially habitable planets, says Burns. High energy cosmic rays from the parent star of exoplanets get trapped in the magnetic fields, causing them to radiate at low radio frequencies, he says. We can potentially detect these polarized radio emissions using arrays of radiotelescopes that we are designing for the far side, Burns notes.
Probing The Cosmic Dark Ages
During the Dark Ages, just before Cosmic Dawn, we believe the Universe was filled with mostly neutral Hydrogen and dark matter, says Hibbard. If we can measure this signal, it could allow us to understand and perhaps characterize dark matter, he says.
Thus, one of the main science drivers for lunar far side radiotelescopes is the study of the cosmological 21-cm signal of neutral hydrogen, says Hibbard. It is in fact the only known probe of the Universe some 100 million years after the Big Bang and before the first luminous objects formed like stars and galaxies, he says.
The Bottom Line?
These observations allow us to test the standard models of cosmology and physics during a unique epoch of the universe uncontaminated by complications produced by feedback from stars and galaxies, says Burns.
