Receiver design for the REACH global 21-cm signal experiment

• Published in: Experimental astronomy 2025, Vol.59 (1), p.7, Article 7
• Main Authors: Roque, Ian L. V., Razavi-Ghods, Nima, Carey, Steven H., Ely, John A., Handley, Will, Magro, Alessio, Chiello, Riccardo, Huang, Tian, Alexander, P., Anstey, D., Bernardi, G., Bevins, H. T. J., Cavillot, J., Croukamp, W., Cumner, J., de Lera Acedo, E., de Villiers, D. I. L., Fialkov, A., Gessey-Jones, T., Gueuning, Q., Josaitis, A. T., Kulkarni, G., Leeney, S. A. K., Maiolino, R., Meerburg, P. D., Mittal, S., Pagano, M., Pegwal, S., Pieterse, C., Pritchard, J. R., Saxena, A., Scheutwinkel, K. H., Scott, P., Shen, E., Sims, P. H., Smirnov, O., Spinelli, M., Zarb-Adami, K.
• Format: Article
• Language: English
• Subjects: Astronomy; Calibration; Chemistry and Earth Sciences; Computer Science; Data analysis; Observations and Techniques; Physics; Physics and Astronomy; Radiometry; Statistics for Engineering
• ISSN: 0922-6435; 1572-9508; 1572-9508
• DOI: 10.1007/s10686-024-09975-3

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.