NenuFAR is a radiointerferometer located at the Station of Radioastronomy in Nancay, France operational since October 2019. It instrument consists in 96 mini-arrays of 19 antennas each, observing in the 40-85 Mhz range (z ~15-31). This frequency range has not yet been probed by highly sensitive astronomical instruments, and Nenufar can either serve as a low-frequency extension of the european instrument LOFAR or as a standalone interferometer.
The NenuFAR Cosmic Dawn Key Project aims at detecting the angular fluctuations of the 21 cm signal in this range. However, the estimated system brightness temperature lies around 10^3 K, while the standard models predict a 21 cm signal at around 10mK. Long observation times and powerful data processing pipelines are therefore required in order to extract the separate the signal from the noise and foregrounds.
500 hours of observations of the North Celestial Pole (NCP) field have already been performed, while another 500 are already scheduled. Observing the NCP requires nearly no beam-tracking and no phase-tracking. This field is also the target of the LOFAR-EoR project and overlaps with the AARTFAACT field, which allow for cross-validation between instruments and improved sky models.
A 1000h observation time of the NCP has been estimated to decrease the amplitude of the thermal noise of the instrument to values low enough to allow the detection of signals consistent with standard models, but non-standard models predict signals that may be detectable within ~100h of observation.
A first measure of the average value of the signal by the EDGES experiment has been announced in 2018 (Bowman et al 2018). The report states that the absorption peak is reached at z~17 and its intensity is anything but attainable by canonical theoretical models and simulations. These observations have not been replicated by the SARAS 3 experiment. A detection of the power spectrum of the signal by NenuFAR could provide a definitive answer to the EDGES puzzle.
Read more about the Cosmic Dawn Key Project : https://arxiv.org/abs/2109.10055
More about NenuFAR : Nenufar website