Observations of the 21-cm line from primordial hydrogen promise to be one of the best tools to study the early epochs of the Universe: the dark ages, the cosmic dawn and the subsequent epoch of reionization. In 2018, the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) caught the attention of the cosmology community with a potential detection of an absorption feature in the sky-averaged radio spectrum centred at 78 MHz. The feature is deeper than expected, and, if confirmed, would call for new physics. However, different groups have re-analysed the EDGES data and questioned the reliability of the signal. The Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) is a sky-averaged 21-cm experiment aiming at improving the current observations by tackling the issues faced by current instruments related to residual systematic signals in the data. The novel experimental approach focuses on detecting and jointly explaining these systematics together with the foregrounds and the cosmological signal using Bayesian statistics. To achieve this, REACH features simultaneous observations with two different antennas, an ultra-wideband system (redshift range about 7.5 to 28) and a receiver calibrator based on in-field measurements. Simulated observations forecast percent-level constraints on astrophysical parameters, potentially opening up a new window to the infant Universe.

对原始氢的 21 厘米线的观测有望成为研究宇宙早期时代的最佳工具之一：黑暗时代、宇宙黎明和随后的再电离时代。2018 年，检测全球再电离时代特征 (EDGES) 的实验引起了宇宙学界的注意，该实验可能检测到以 78 MHz 为中心的天空平均无线电频谱中的吸收特征。该特征比预期的要深，如果得到证实，将需要新的物理学。然而，不同的团体重新分析了 EDGES 数据并质疑信号的可靠性。用于分析宇宙氢的无线电实验 (REACH) 是一项 21 厘米的天空平均实验，旨在通过解决当前仪器面临的与数据中残留系统信号相关的问题来改进当前的观测。新的实验方法侧重于使用贝叶斯统计检测和共同解释这些系统学以及前景和宇宙学信号。为了实现这一点，REACH 采用两个不同的天线同时观测，一个超宽带系统（红移范围约为 7.5 到 28）和一个基于现场测量的接收器校准器。模拟观测预测天体物理参数的百分比水平限制，可能为婴儿宇宙打开一个新窗口。新的实验方法侧重于使用贝叶斯统计检测和共同解释这些系统学以及前景和宇宙学信号。为了实现这一点，REACH 采用两个不同的天线同时观测，一个超宽带系统（红移范围约为 7.5 到 28）和一个基于现场测量的接收器校准器。模拟观测预测天体物理参数的百分比水平限制，可能为婴儿宇宙打开一个新窗口。新的实验方法侧重于使用贝叶斯统计检测和共同解释这些系统学以及前景和宇宙学信号。为了实现这一点，REACH 采用两个不同的天线同时观测，一个超宽带系统（红移范围约为 7.5 到 28）和一个基于现场测量的接收器校准器。模拟观测预测天体物理参数的百分比水平限制，可能为婴儿宇宙打开一个新窗口。