A tiny digital receiver system based on a compact single-board computer about the size of a credit card could now help us unravel the mysteries of the Cosmic Dawn, when the very first stars flickered to life.

The cosmic dawn is when the first stars and galaxies formed in the Universe, significantly altering the course of its evolution. Scientists believe this mysterious epoch holds the key to understanding the Universe as we see it today, making it an irresistible frontier for discovery. However, very little is known about this period due to a lack of precise observations.

Read in Hindi: अब आसानी से खुलेंगे ‘कॉस्मिक डॉन’ के रहस्य

The first of its kind proposed space payload, PRATUSH, i.e. Probing Reionisation of the Universe using Signal from Hydrogen, by a team from Raman Research Institute, an autonomous institute funded by the Department of Science and Technology, is designed to unlock this mystery. It is a future radiometer in lunar orbit that will answer questions about the first stars formed in our universe.

In keeping with space science's long-standing focus on low-mass, high-capability payloads, PRATUSH demonstrates how a compact controller can shoulder precision radio measurements.

This can help detect a faint radio signal emitted from hydrogen atoms, which carries imprints of several events of the Cosmic Dawn. Capturing this signal is like hearing a whisper in a stadium full of noise because it is buried under interference, millions of times stronger than the signal itself.

On Earth, this whisper from the past is drowned out by radio noise and interference such as FM transmissions. PRATUSH, therefore, ultimately envisions a lunar far-side mission, which is expected to be the most radio-quiet place in the inner Solar System, free from Earth's interference and ionospheric distortion.

The PRATUSH team has built a laboratory model of their radiometer to demonstrate its suitability for detecting the faint cosmological signal. The radio signals are captured by the antenna, amplified by the analog receiver, and turned into digital data by the digital receiver. An advanced chip called a Field Programmable Gate Array then processes this data, converting it into fine fingerprints representing how bright the sky is at different radio frequencies. Considering the stringent requirements of space payload, including size, weight, and power constraints, the PRATUSH team has developed a digital receiver system based on a compact single-board computer built around a Raspberry Pi.

It acts as the master conductor of PRATUSH’s radiometer and coordinates the antenna, receiver, and a powerful chip called an FPGA that processes streams of cosmic radio data. The SBC not only records and stores this information but also performs crucial calibrations and ensures everything runs smoothly, capturing high-speed data streams and carrying out preliminary data processing. In the flight model commercial Raspberry-Pi can be replaced by a space-qualified counterpart.

"SBCs, as scaled-down versions of desktop or laptop computers, deliver an appealing balance of size, performance, and efficiency to manage the data generated by FPGAs through software instructions," said Girish BS, Research Scientist E, Electronics Engineering Group, Raman Research Institute.

Performance tests confirm that this minimalist strategy is highly effective. With 352 hours of data collection on a reference signal, the receiver's noise was reduced to an extremely low level, demonstrating its sensitivity to detect the faint Cosmic Dawn signal. With newly implemented software enhancements and next-generation space-grade devices, the system is on track for even greater performance, ensuring data integrity.

The SBC is a critical component of the digital receiver system for PRATUSH, carefully selected to serve as both the master controller and data recorder," said Srivani KS, Research Scientist E, Electronics Engineering Group, Raman Research Institute.

By substituting traditional solutions with a low-power SBC, PRATUSH reduces weight, power usage, and sophistication, all critical considerations for space missions. It makes putting a highly sensitive radiometer into lunar orbit much more realistic.

"Technologies like the SBC-based digital receiver will be an integral part of payloads to detect the signal of the Cosmic Dawn from one of the quietest corners of the solar system," said Saurabh Singh and Mayuri S Rao, Associate Professors, Astronomy & Astrophysics, Raman Research Institute.

PRATUSH may unlock how the first stars sculpted the Universe and even potentially discover new physics. Behind the success of this endeavour may lie a humble bit of technology, a small computer serenely masterminding one of humanity's most ambitious efforts to hear the Universe's earliest whispers.