Jaime Álvarez-Muñiz, Rafael Alves Batista, A. Benoit-Lévy, Teresa Bister, M Boháčová, Mauricio Bustamante, W. Carvalho, Yu Chen, L. Cheng, S. Chiche, J.M. Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zi-Gao Dai, R.M. de Almeida, Beatriz de Errico, A. De Roeck, K. D. de Vries, Valentin Decoene, Peter B. Denton, Bin Duan, Bohao Duan, R. Engel, William Erba, Y Fan, Arsène Ferrière, J.P. Góngora, Q. B. Gou, Q. B. Gou, Marion Guelfand, Gang Guo, Jian‐Hua Guo, Jian‐Hua Guo, Claire Guépin, Lukas Gülzow, A. Haungs, Matej Havelka, H. He, E. Hivon, Hongbo Hu, G Q Huang, X. T. Huang, Xiaoyuan Huang, T Huege, Wei Jiang, Shinsuke Kato, R Koirala, Kumiko Kotera, J. Köhler, Bruno L. Lago, Zhiping Lai, Jolan Lavoisier, F. Legrand, A. Leisos, Rui Li, Xiaonan Li, Xingyu Li, Ruo-Yu Liu, Ruo-Yu Liu, Peng-Xiong Ma, Oscar Macías, F. Magnard, A. Marcowith, O. Martineau‐Huynh, Zachary Mason, T. McKinley, Paul Minodier, M Mostafa, K. Murase, V. Niess, Stavros Nonis, S. Ogio, F. Oikonomou, H. Pan, K Papageorgiou, T. Pierog, L. W. Piotrowski, S. Prunet, C. Prévotat, Xiangli Qian, M. Roth, T. Sako, Sachin M. Shinde, D. Szálas-Motesiczky, S. Sławiński, Kaoru Takahashi, Xishui Tian, Charles Timmermans, Petr Tobiška, A. Tsirigotis, Matias Jorge Tueros, G. Vittakis, V. Voisin, Hanrui Wang, Hanrui Wang, Shen Wang, Shen Wang, Xiangyu Wang, Da-Ming Wei, Da-Ming Wei
Abstract The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of Ultra-High-Energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interactions like gamma rays and neutrinos. The GRAND Collaboration plans to achieve this using large arrays of radio antennas that look for the radio signals emitted by the air showers initiated by the interactions of the UHE particles in the atmosphere. Since 2023, three small-scale prototype GRAND arrays have been in operation: GRAND@Nançay in France, GRAND@Auger in Argentina, and GRANDProto300 in China. Together, their goal is to validate the detection principle of GRAND under prolonged field conditions, achieving efficient, autonomous radio-detection of air showers. We describe the hardware, software, layout, and operation of the GRAND prototypes. Using their data, we show a first characterization of the local electromagnetic environment of each site and a measurement of the Galactic synchrotron emission. Despite challenges, the successful operation of the prototypes confirms that the GRAND instrumentation is apt to address the goals of the experiment and lays the groundwork for its ensuing stages.