Technology
Overview
REACH is a global 21‑cm radiometer designed to detect the faint, redshifted hydrogen signal from the Cosmic Dawn and Epoch of Reionization. Operating between 50 and 200 MHz, REACH combines ultra‑smooth wideband antenna designs, precision radiometry, and advanced Bayesian calibration to overcome the ∼100,000‑times‑brighter galactic foregrounds and challenging environmental conditions.
A multi-antenna system
Using several antennas at once lets you cross‑check and average their measurements, reducing random noise and instrumental quirks. It also provides slightly different “views” of the sky, which helps pinpoint and remove local interference or systematics. Overall, this boosts the confidence and clarity of the faint cosmological signal you’re hunting. We have planned for a maximum of 5 radio antennae operating simultaneously, including systems deployed at 2 different locations in the Southern and Northern hemispheres.
Front-end receiver
The front‑end enclosure houses a precision low‑noise amplifier (LNA) and built‑in calibrators, switching between sky and hot/ambient loads right at the antenna to track and remove system drifts. Active thermal control keeps calibration loads at stable temperatures, ensuring millikelvin‑level accuracy in the gain and noise measurements.
Digital back-end
An RFoF optical link transmits the amplified RF signal over 120 m of single‑mode fibre, preserving signal integrity with minimal added noise for digital back‑end processing. A high resolution (12 KHz channels) SanitasEG iTPM spectrometer computes power spectral densities in real time, while Pico TC‑08 thermocouples monitor calibrator temperatures in the front-end, feeding comprehensive data into the Bayesian calibration pipeline. We have developed all our own control and monitor software, allowing us to run continuous semi-automatic observations every night.
A stand-alone telescope
The observing system is a completely self‑contained and off-the-grid design. It operates independently in the field—needing only solar power and a satellite data link—so we can deploy it in remote, RFI‑quiet sites without extra infrastructure.
A super brain
The data is sent from the Karoo back to Cambridge using a commercial satellite link, where the REACH team uses the University of Cambridge's state-of-the-art HPC system. "CSD3" delivers over 10 petaflops of compute power to academic researchers and industry partners, REACH amongst them.