Africa2Moon, the African radio telescope selected to fly to the lunar south pole on China’s Chang’e‑8 mission in 2029, has had its design published in Nature Astronomy, revealing a novel approach: three self‑contained spherical receivers that will roll across the lunar surface and spread apart to form a single radio interferometer.
How the instrument works
The demonstrator array is composed of three units described in the paper as Bounced African Low Lunar Spheres, or Balls. Each sphere is roughly 30cm across, weighs under 4kg and contains:
- three concentric orthogonal loop antennas;
- eight solar panels;
- a contained electronics box functioning as an independent radio receiver.
Once deployed, the spheres are designed to roll freely across the lunar terrain, increasing the separation between them until they form the baseline of a functioning interferometer. The array is expected to operate for at least six Earth days, during which it will observe the Earth, the Sun, the Galaxy and the lunar surface itself.
“Bounced African Low Lunar Spheres, or Balls”
Science goals and the SETI angle
Alongside astronomical and lunar studies, the instrument will search for technosignatures — signals that could indicate artificial sources beyond Earth. The inclusion of a SETI‑style observation programme is notable: previous public descriptions of the mission did not indicate an explicit search for technosignatures.
The paper emphasises an important operational distinction for lunar radio astronomy. The far side of the Moon is radio‑quiet and shielded from human‑made radio noise and, at night, the Sun. However, this demonstrator will land at the lunar south pole, where the Earth remains in view. That geometry partly explains why Earth will be a target of observations from this initial deployment. The full mission concept envisages a larger array on the far side with 55 antennas — one for each African nation.
South African involvement
Rhodes University has a prominent role in the published work. Distinguished professor Oleg Smirnov, who holds the SARAO research chair in radio astronomy techniques and technologies, is named principal investigator for radio astronomy. His group, the Centre for Radio Astronomy Techniques and Technologies, has worked for more than a decade on the specific technical problems this mission addresses.
Implications and context
The Africa2Moon demonstrator is a proof‑of‑concept for a lunar surface interferometer assembled from compact, mobile receivers. If successful, it would be the first radio interferometer to operate on the lunar surface, paving the way for larger, more sensitive arrays in future missions. It also places African research teams at the centre of an international lunar science effort.
There are practical limitations and trade‑offs in this first mission: the south polar landing site offers partial sky access and continuous solar power opportunities for some locations, but it does not provide the radio silence of the far side. As the paper notes, the full scientific advantages of a far‑side array would require future deployments when logistical and geopolitical conditions permit.
What to watch next
- Technical tests and integration results ahead of the 2029 Chang’e‑8 launch;
- Mission plans and timelines for the eventual far‑side array with 55 antennas;
- Research outputs from the demonstrator, including results from the technosignature search.
The published design offers a concrete snapshot of a mission that blends engineering ingenuity with ambitious continental scientific goals. For South African radio astronomy, the project reinforces existing strengths in instrumentation and technique development and promises new opportunities for researchers and students to participate in lunar science.
