PRATUSH (Probing Reionisation of the Universe using Signal from Hydrogen)

India is preparing to take a significant leap in astrophysics and cosmology with PRATUSH (Probing Reionisation of the Universe using Signal from Hydrogen), an innovative lunar-orbit mission being developed by the Raman Research Institute (RRI), Bengaluru. Designed to detect the faint 21-cm hydrogen signal from the early Universe, PRATUSH aims to unravel mysteries surrounding the Cosmic Dawn—the epoch when the first stars and galaxies were born.

This mission reflects India’s growing role in frontier space science, expanding beyond planetary exploration to answer fundamental questions about the origin of the Universe.

What is PRATUSH?

• Full Form: Probing Reionisation of the Universe using Signal from Hydrogen

• Type: Lunar-orbit radiometer experiment

• Developed by: Raman Research Institute (RRI), Bengaluru

• Deployment Site: Lunar far side, chosen for its radio-quiet environment (free from Earth’s radio frequency interference)

• Objective: To detect the faint 21-cm hydrogen line from the Cosmic Dawn and the Epoch of Reionisation (EoR)

Why the 21-cm Hydrogen Signal Matters?

The 21-cm hydrogen line is a faint radio signal emitted by neutral hydrogen atoms in the early Universe. Detecting it is like tuning into a cosmic “fossil record” that carries information about:

• The Cosmic Dawn (when the first stars ignited, around 180–200 million years after the Big Bang).

• The Epoch of Reionisation (EoR) (when starlight ionised hydrogen, shaping the transparent Universe we see today).

• The evolution of matter, structure formation, and the role of dark matter in the early Universe.

If successful, PRATUSH will allow Indian scientists to directly observe signals from an era never seen before.

Technology Behind PRATUSH

PRATUSH integrates a sophisticated radiometer system with advanced electronics to ensure precision detection of faint cosmic signals.

• Radiometer: Measures radio emissions at the 21-cm wavelength.

• Antenna System: Captures faint hydrogen signals.

• Analogue Receiver: Converts radio signals into measurable electronic signals.

• Digital Receiver & FPGA Chip: Processes large volumes of raw data for high-accuracy detection.

• Single-Board Computer (SBC): Similar to a Raspberry Pi, controls the system, performs calibration, and processes data before transmission.

The lunar far side provides an ideal observation platform as it is shielded from Earth’s radio noise, enabling clearer measurements than any ground-based experiment.

PRATUSH and SARAS: Complementary Missions

PRATUSH builds on the experience of SARAS (Shaped Antenna measurement of the background Radio Spectrum), a ground-based radiometer experiment also developed by RRI.

• SARAS: Operates from Earth to detect the 21-cm hydrogen signal but faces challenges due to terrestrial radio interference.

• PRATUSH: Moves the experiment into lunar orbit, especially the far side of the Moon, where interference is minimal, ensuring better sensitivity and accuracy.

Together, SARAS and PRATUSH form a progressive chain of experiments to unlock the cosmic history of the Universe.

Why Place PRATUSH on the Lunar Far Side?

1. Radio Quietness: Shielded from Earth’s constant radio interference.

2. Stable Observations: No atmosphere to distort signals.

3. Deep Space Advantage: Provides the cleanest possible window to probe faint 21-cm signals.

This strategy places India alongside global efforts like NASA’s proposed Lunar Crater Radio Telescope (LCRT) and China’s Chang’e-based astronomy experiments, boosting India’s visibility in international astrophysics research.

Scientific Significance of PRATUSH

• Exploring the Cosmic Dawn: Directly studying when the first stars and galaxies were born.

• Understanding Reionisation: Mapping how the Universe transitioned from dark, neutral hydrogen gas to the ionised state we observe today.

• Dark Matter Clues: Early Universe hydrogen signals may offer indirect hints about the role of dark matter in cosmic evolution.

• Indian Leadership in Space Science: Strengthens India’s presence in cutting-edge astrophysics, complementing ISRO’s planetary and space missions.

Conclusion

The development of PRATUSH highlights India’s ambition to explore the deepest epochs of the Universe’s history. By moving a sophisticated radiometer to the lunar far side, RRI scientists aim to detect the elusive 21-cm hydrogen signal that carries the story of the Cosmic Dawn.

With its foundation built upon the SARAS experiment, PRATUSH represents a bold leap into lunar-based cosmology and places India on the global map of next-generation astrophysics research.

As India advances in space exploration, PRATUSH not only deepens our cosmic understanding but also strengthens the country’s role as a pioneer in science beyond Earth.

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