Examine India's contribution to lunar-based astronomy research through missions such as PRATUSH, and its significance for understanding the early universe.

Earth's radio noise and ionosphere drown out the faint 21-cm signal of neutral hydrogen from the "Cosmic Dawn", making the Moon's far side the most radio-quiet site in the inner Solar System [1]. India's entry into this frontier is PRATUSH, a proposed lunar radiometer that marks a shift from lunar exploration to lunar-based astronomy.

India's contribution through PRATUSH

• PRATUSH (Probing ReionizATion of the Universe using Signal from Hydrogen) is a radiometer conceived by the Raman Research Institute (RRI), Bengaluru, an autonomous institute funded by the Department of Science and Technology [1].
• Design: orbiting the Moon, it will measure the low-frequency radio sky (roughly 40–200 MHz), observing only when shielded behind the far side and downlinking data from the near side [2].
• It builds on RRI's indigenous heritage in SARAS, India's ground-based 21-cm spectral radiometer — a rare instance of home-grown observational cosmology [2].

Technological and institutional significance

• Demands self-calibrating receivers and compact, low-power onboard computing capable of precision measurement under strict mass-power budgets [1].
• Leverages ISRO's demonstrated lunar access after Chandrayaan-3's soft landing, giving credible launch and deep-space communication backing to science payloads [3].

Significance for understanding the early universe

• The 21-cm signal is the only observational probe of the Dark Ages and Cosmic Dawn — the era before the first stars and galaxies formed [2].
• Its detection would constrain models of reionization, early structure formation and dark matter, complementing the Cosmic Microwave Background, which maps a much earlier epoch.

Limitations

• PRATUSH remains in the pre-project studies phase, not an approved mission [4]; the target signal is thousands of times weaker than galactic foregrounds, making extraction the central challenge.

India's contribution today is conceptual and technological rather than operational, yet it places the country among the few pursuing far-side cosmology. Timely project approval, sustained DST–ISRO coordination and international data-sharing can convert PRATUSH into a genuine leap for Indian basic science.