From moon’s far side, a satellite to look for the first radio signal
The 21-cm radio signal emitted by neutral hydrogen is like the proverbial needle in a haystack as it is buried beneath foreground radio emissions thousands of times stronger. To isolate it and reveal how the first stars and galaxies formed is a great challenge even for advanced platforms like the planned CosmoCube and India’s PRATUSH
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Context
Scientists from the plan to launch the CosmoCube satellite to the far side of the Moon within this decade. The mission aims to utilize the Moon as a natural shield against Earth's radio interference to detect faint radio signals from the early universe, specifically from neutral hydrogen atoms, to understand the 'Cosmic Dark Ages'. This aligns with India's proposed mission, which shares a similar objective.
UPSC Perspectives
Scientific Research
The CosmoCube mission highlights the critical need for radio-quiet environments in modern astronomy. The far side of the Moon, which permanently faces away from Earth, offers an unparalleled natural shield from anthropogenic (human-caused) radio frequency interference (RFI) originating from terrestrial communications and broadcasting. This radio-quiet zone is essential for detecting the extremely faint 21-cm signal emitted by neutral hydrogen atoms during the Cosmic Dark Ages—the period after the but before the first stars formed. By measuring this signal at low frequencies (10-100 MHz), scientists hope to capture the 'fingerprint' of early hydrogen, providing a window into an era currently unobservable by optical telescopes or the Cosmic Microwave Background (CMB). The difficulty lies in isolating this signal, described as a 'needle in a haystack', from foreground radio emissions that are orders of magnitude stronger.
Cosmological Exploration
CosmoCube aims to address profound questions in cosmology, particularly the Hubble tension—the discrepancy in the universe's expansion rate measured using local celestial objects versus the early universe's CMB. By examining the unexplored epoch between the CMB emission and the Era of Reionisation (when the first stars ionized neutral hydrogen, making the universe transparent), CosmoCube could provide independent data to test new physics models. These models might involve modifications to early expansion history, additional radio backgrounds, or novel interactions between ordinary matter and Dark Matter (which constitutes over 80% of the universe's mass but does not interact with light). Understanding these phenomena is crucial for a complete timeline of cosmic evolution.
Indian Space Endeavours
The article's mention of India's (Probing ReionisATion of the Universe using Signal from Hydrogen) emphasizes 's growing ambition in deep space exploration and astrophysics. , a proposed radio telescope intended for lunar orbit, shares the objective of studying the Cosmic Dawn by detecting the 21-cm hydrogen signal from the Moon's far side. This underscores India's active participation in cutting-edge global astronomical research, moving beyond planetary exploration (like ) to fundamental cosmology. The success of such missions requires sophisticated technology, specifically highly sensitive and accurately calibrated radio receivers (radiometers), capable of operating in challenging space environments while remaining radio-silent during data collection to avoid self-contamination.