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Tiny satellite will use the dark side of the Moon as a shield
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A tiny UK-built satellite, about the size of a carry-on suitcase, will probe one of cosmology's greatest mysteries: the cosmic dark ages. Named CosmoCube, it will use the Moon's far side as a natural shield to detect a faint hydrogen signal from before the first stars. The mission, led by the University of Cambridge, has UK Space Agency funding and could launch within five years.
The signal, the 21-centimetre line, was emitted by neutral hydrogen during the period between the Big Bang's afterglow and Cosmic Dawn, spanning roughly 150 million years. No one has directly observed this era before. Earth-based telescopes cannot detect it because the ionosphere blocks the frequencies, and human-made radio interference drowns out the whisper.
CosmoCube's lunar orbit offers a unique solution. For about 40 minutes of each two-hour orbit, the satellite will be shielded from Earth's noise behind the Moon. Over its two-year mission, it will gather 1,000 hours of data, helping explain how the universe transitioned from darkness to complexity.
The satellite will operate at 10β50 MHz, far beyond ground-based telescopes' range. It will unfold a lightweight antenna and use a 'Dicke-switched' calibrator to cancel internal noise. Back on Earth, Bayesian statistical methods will remove foreground emissions from our galaxy.
Lead author Professor Eloy de Lera Acedo said the far side is the 'only option' and a 'fortress of solitude.' The compact, low-cost platform is unique, and the mission will also explore dark matter's role in forming the first stars and galaxies.
The study appears in Nature Astronomy. Other missions from the US, India and others are planned, meaning the Moon's quiet side may not stay quiet for long. CosmoCube's timely launch could secure access to this pristine environment.
