Short-lived Experiment Marks Start of Radio Astronomy from the Moon

After a half-century hiatus, in February NASA finally returned to the lunar surface with a scientific payload. It did so by piggybacking on the Odysseus lander, the first of the NASA-sponsored privately operated missions.

The first mission of the agency’s Commercial Lunar Payload Services program, which was designed to cut costs and accelerate lunar research, didn't go exactly as planned, however. A malfunction of the navigation system resulted in the spacecraft hitting the ground harder than expected. One  of the lander’s legs broke and the spacecraft tipped over, ending up at an awkward 30-degree tilt.

Despite the setback, the scientific experiment that the lander carried, called Radio wave Observations at the Lunar Surface of the photo Electron Sheath (ROLSES), returned data, and researchers on Earth are squeezing as much out of it as they can.

“All was not lost,” said instrument co-investigator, Jack Burns (University of Colorado, Boulder), during a press conference at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin. Burns confirmed that ROLSES became the first radio astronomy experiment to work on the Moon, where it served as a precursor to future, more advanced lunar radio telescopes. The team even managed to collect some unplanned scientific measurements on the journey to the Moon.

The experiment had a set of four wire antennas and a radio spectrometer, weighing only 4 kilograms (9 pounds) in all. The team designed it with the purpose of investigating how the Moon’s porous surface scatters cosmic radio waves. ROLSES landed in the Malapert A Crater, near the south pole of the lunar nearside.

The ROLSES team ended up with two opportunities to collect data. The first occurred when an unexpected glitch resulted in one of the 2.5-meter (8-foot) antennas deploying midflight, when the spacecraft was still 10,000 km (6,000 miles) away from the Moon. The antenna can be seen sticking out into space in the images taken by Odysseus’s onboard cameras.

“We took advantage of that and turned on our radio spectrometer and got some data,” Burns said. With about 1½ hours of data, the researchers clearly detected Earth’s radio emissions, which come from human activity. “We got a good [frequency] selfie of the Earth taken from a unique perspective,” Burns added.

The glitch allowed ROLSES to record Earth’s radio emissions from a distance, an unexpected repetition of an experiment Carl Sagan concocted back in 1993. Sagan used the Galileo spacecraft on its way to Jupiter to obtain a similar observation of Earth; however, ROLSES data is more exhaustive than what Galileo could gather at the time, with better time resolution and higher frequencies.

Studying Earth in this way provides a reference point for future lunar telescopes’ detection of exoplanet signals. Our planet’s reference point might even allow the identification of possible technosignatures, the signals extraterrestrial civilizations might produce.

ROLSES’s second opportunity for data collection came after the lunar landing. The original experiment called for eight days’ of data collection, but the angle of the spacecraft severely shortened that time to only 20 minutes. Nevertheless, the device was able to deploy its antennas, gather some data, and return it to Earth.

Despite the setbacks, Burns remains optimistic — the instrument is getting a second chance. NASA has already greenlit an upgraded ROLSES-2 experiment that will fly in on another commercial lander in 2026.