Receiver design for the REACH global 21-cm signal experiment

Ian L V Roque; Nima Razavi-Ghods; Steven H Carey; John A Ely; Will Handley; Alessio Magro; Riccardo Chiello; Tian Huang; P Alexander; D Anstey; G Bernardi; H T J Bevins; J Cavillot; W Croukamp; J Cumner; E de Lera Acedo; D I L de Villiers; A Fialkov; T Gessey-Jones; Q Gueuning; A T Josaitis; G Kulkarni; S A K Leeney; R Maiolino; P D Meerburg; S Mittal; M Pagano; S Pegwal; C Pieterse; J R Pritchard; A Saxena; K H Scheutwinkel; P Scott; E Shen; P H Sims; O Smirnov; M Spinelli; K Zarb-Adami

doi:10.1007/s10686-024-09975-3

Receiver design for the REACH global 21-cm signal experiment

Exp Astron (Dordr). 2025;59(1):7. doi: 10.1007/s10686-024-09975-3. Epub 2025 Jan 17.

Authors

Ian L V Roque^{1

2}, Nima Razavi-Ghods¹, Steven H Carey¹, John A Ely¹, Will Handley^{1

2}, Alessio Magro³, Riccardo Chiello⁴, Tian Huang¹, P Alexander¹, D Anstey^{1

2}, G Bernardi^{5

6

7}, H T J Bevins^{1

2}, J Cavillot⁸, W Croukamp⁹, J Cumner^{1

2}, E de Lera Acedo^{1

2}, D I L de Villiers⁹, A Fialkov^{2

10}, T Gessey-Jones^{1

2}, Q Gueuning¹, A T Josaitis¹, G Kulkarni¹¹, S A K Leeney^{1

2}, R Maiolino^{1

2}, P D Meerburg¹², S Mittal¹¹, M Pagano^{13

14}, S Pegwal⁹, C Pieterse⁹, J R Pritchard¹⁵, A Saxena¹², K H Scheutwinkel^{1

2}, P Scott¹, E Shen¹, P H Sims^{13

14}, O Smirnov^{6

7}, M Spinelli^{16

17

18}, K Zarb-Adami^{3

4}

Affiliations

¹ Cavendish Astrophysics, University of Cambridge, Cambridge, UK.
² Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK.
³ Institute of Space Sciences and Astronomy, University of Malta, Msida, Malta.
⁴ Physics Department, University of Oxford, Oxford, UK.
⁵ Istituto di Radioastronomia, Istituto nazionale di astrofisica, Bologna, Italy.
⁶ Department of Physics and Electronics, Rhodes University, Grahamstown, South Africa.
⁷ South African Radio Astronomy Observatory, Cape Town, South Africa.
⁸ Antenna Group, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
⁹ Department of Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch, South Africa.
¹⁰ Institute of Astronomy, University of Cambridge, Cambridge, UK.
¹¹ Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai, India.
¹² Faculty of Science and Engineering, University of Groningen, Groningen, Netherlands.
¹³ Trottier Space Institute, McGill University, Montréal, Canada.
¹⁴ Department of Physics, McGill University, Montréal, Canada.
¹⁵ Department of Physics, Imperial College London, London, UK.
¹⁶ Osservatorio Astronomico di Trieste, Istituto nazionale di astrofisica, Trieste, Italy.
¹⁷ Institute of Fundamental Physics of the Universe, Trieste, Italy.
¹⁸ Department of Physics and Astronomy, University of the Western Cape, Bellville, South Africa.

Abstract

We detail the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to highly-calibratable system development. Following this, we share laboratory results based on the calculation of noise wave parameters utilising an over-constrained least squares approach. For five hours of integration on a custom-made source with comparable impedance to that of the antenna used in the field, we demonstrate a calibration RMSE of 80 mK. This paper therefore documents the state of the calibrator and data analysis in December 2022 in Cambridge before shipping to South Africa.

Keywords: Calibration; Cosmology; Dark ages; Instrumentation; Radiometer; Reionisation.