The Dark-Ages Explorer (DEX): design and development of a lunar far side radio interferometer for neutral hydrogen cosmology observations

The Dark Ages Explorer (DEX) is the European initiative for a radio interferometry facility on the lunar far side. DEX will focus on performing neutral hydrogen cosmology observations, aiming to obtain the spatial power spectrum of density fluctuations throughout the history of the early Universe. DEX is planned to consist of a large number (≥1024) of planar antenna elements deployed onto the lunar surface around the landing site, providing a densely filled aperture. The antenna elements are arranged in a regular grid, making it possible to generate sky snapshots by using the efficiency of a spatial 2D Fourier transform for every frequency bin. This talk introduces the concept design of DEX, shows the expected performance of the array in the presence of lunar regolith and discusses current and future efforts in technology development that are required to realise this design.