When Intuitive Machines' Odysseus Lander launched for the Moon in February 2024, it faced a number of problems. While orbiting the Moon and preparing to land, its laser navigation system went offline. The 1,900 kg spacecraft had to rely on navigation cameras to land.
When it reached the surface on February 22nd, 2024, it became the first US spacecraft to soft land on the Moon since Apollo 17 in 1972. Unfortunately, upon landing, Odysseus broke one of its six legs and ended up perched at a 30-degree angle. This made it difficult for the spacecraft to transmit data back to Earth.
Despite this, Intuitive Machines declared the mission a success. The Radiowave Observations on the Lunar Surface of the photo-Electron Sheath instrument (ROLSES1) was able to do its job. According to NASA, ROLSES1 is a low-frequency radio spectrometer designed to study "the photoelectron sheath density and scale height near the lunar surface." In essence, it's a radio telescope, and it became the first radio astronomy experiment to work on the Moon.
New research submitted to The Astrophysical Journal presents the results from ROLSES1's observations from the lunar surface. Its title is "Results from NASA's First Radio Telescope on the Moon: Terrestrial Technosignatures and the Low-Frequency Galactic Background Observed by ROLSES-1 Onboard the Odysseus Lander." Joshua Hibbard, the lead author, is from the Center for Astrophysics and Space Astronomy in the Department of Astrophysical and Planetary Science at the University of Colorado in Boulder.
"Radiowave Observations on the Lunar Surface of the photo-Electron Sheath instrument (ROLSES1) onboard the Intuitive Machines' Odysseus lunar lander represents NASA's first radio telescope on the Moon, and the first United States spacecraft landing on the lunar surface in five decades," the authors write. "Despite a host of challenges, ROLSES-1 managed to collect a small amount of data over fractions of one day during cruise phase and two days on the lunar surface with four monopole stacer antennas that were in a non-ideal deployment."
ROLSES-1 managed to collect some data while en route to the Moon when one of its four simple antennae unexpectedly deployed during flight.
One of ROLSES-1's four antennae unexpectedly deployed during flight and was able to collect some data. Image Credit: Intuitive Machines.
Once on the lunar surface, ROLSES-1 collected more data with additional antennae in two short, distinct periods. While it was initially expected to gather data for about eight days, it worked for only about 20 minutes combined. What data did it gather, and why is it important?
This figure shows ROLSES-1's view of Earth during its three operating periods: In Transit, Lunar Surface 1 (02/26/24), and Lunar Surface 2 (02/27/24). Note that the entire North American continent is in view during the In-Transit observations, while two large bodies of water (the Pacific and Atlantic oceans) are largely in view during the subsequent two observation days.
The instrument was designed to understand how radio waves are scattered by the Moon's porous surface. It was to observe the Moon's surface environment in radio frequencies, including the important 21 cm line or hydrogen line. The goal was to understand the lunar environment and how it will affect future radiotelescopes on the Moon. It was also built to observe Earth's technosignatures and use it as a reference point in the search for alien technosignatures.
The left panel is the final image transmitted by Odysseus. The right panel shows how the lander is oriented to the lunar surface. Image Credit: (L) Intuitive Machines. (R) Hibbard et al. 2025.
The researchers explain that the instrument was able to detect short-wave transmissions from Earth and satellites orbiting Earth that broke through the ionosphere, writing that these are basically technosignatures. "All antennas recorded shortwave radio transmissions breaking through the Earth's ionosphere—or terrestrial technosignatures—from spectral and raw waveform data," the authors explain. These observations also gathered valuable data on how Earthly radio waves propagate through the ionosphere and reach the Moon, another of the instrument's goals.
It was a good opportunity to examine how our technosignatures appear from an external viewpoint. The authors explain that "technosignatures appear to be modulated by density fluctuations in the Earth’s ionosphere and could be used as markers when searching for extraterrestrial intelligence from habitable exoplanets."
"All was not lost," said study co-author and ROLSES-1 principal investigator Jack Burns at the 224th Meeting of the American Astronomical Society in June 2024. "We got a good [frequency] selfie of the Earth taken from a unique perspective."
ROLSES-1 is just the first of several radio telescopes NASA hopes to send to the lunar surface in the coming years. "ROLSES-1 represents a trailblazing effort to place radio telescopes on the lunar surface for NASA, and through the CLPS program, several other radio telescopes are scheduled to land on the Moon within the next several years," the authors write.
ROLSES-2 is the successor to ROLSES-1 and will be upgraded to gather more precise measurements. It will also be better shielded from interference and better protected from lunar temperature extremes. It will also focus more intently on the 21 cm line.
LuSEE-Night (Lunar Surface Electromagnetics Experiment-Night) will detect the very faint radio waves from the Universe's Dark Ages before the first stars and galaxies formed. It, too, will focus on the all-important 21 cm hydrogen line. LuSEE-Night will be positioned on the lunar far side, where it is exceptionally radio-quiet. Scientists are hopeful that LuSEE-Night will show how long-duration radio astronomy can be conducted on the surface of the Moon.
"ROLSES2 and LuSEE-Night, both lunar radio telescopes launching later in the decade, will have significant upgrades from ROLSES-1 and will be set to take unprecedented measurements of the low-frequency sky, lunar surface, and constrain the cosmological 21-cm signal."
The ultimate goal for lunar radio astronomy is a large parabolic antenna of the type we build on Earth. There are different ideas for this, including FARSIDE (Farside Array for Radio Science Investigations of the Dark Ages and Exoplanets) and the Lunar Crater Radio Telescope.
"In defiance of a litany of obstacles, the Intuitive Machines lunar lander Odysseus landed on the South pole of the Moon near crater Malapert A," the authors write in their conclusion.
Intuitive Machines chose the Malapert A crater because it seemed safe. Image Credit: Intuitive Machines.
ROLSES-2 will launch in about two years and should gather even better measurements of the low-frequency radio sky, the lunar environment, solar bursts, and other phenomena. "ROLSES-2 will perhaps be able to stand tall upon the leaning shoulders of ROLSES-1," the authors write.
LuSEE-Night should launch in 2026. ROLSES-1's observations, as limited as they are, will help both of its successor missions.