Architecture Design and Ground Performance of Netherlands‐China Low‐Frequency Explorer

The Netherlands‐China Low‐Frequency Explorer (NCLE) (Boonstra et al., 2017, https://www.ursi.org/proceedings/procGA17/papers/Paper_J19‐2(1603).pdf; Chen et al., 2020, https://ui.adsabs.harvard.edu/abs/2020AAS…23610203C/abstract) is a radio instrument for astrophysical studies in the low‐frequency range (80 kHz–80 MHz). As a technology demonstrator, NCLE shall inform the design of future radio receivers that aim at low‐frequency radio astronomy. NCLE can make observations at very high spectral resolution (<1 kHz) and generate radio sky maps at an angular resolution of ≈1.5 radians. NCLE uses three monopole antennas, each 5 m long, and three identical analog signal chains to process the signal from each antenna. A single digital receiver samples the signal and calculates the auto‐correlated and cross‐correlated spectra. The instrument's analog and digital signal chains are extensively configurable. They can be fine‐tuned to produce broadband spectra covering the instrument's complete operating frequency range or sub‐bands. NCLE was developed within a veryshort timescale of 2 years, and currently, it is on board Queqiao, the relay spacecraft of the Chang'e‐ 4 mission, in a halo orbit around the Earth‐Moon L2 point. This paper outlines the science cases, instrument architecture with focus on the signal chain, and discusses the laboratory measurements during the pre‐launch phase. Radio observations from the Moon at very low frequenciesRadio instrument technology demonstration for future lunar observatory and interferometryRadio receiver design for low‐frequency observation Radio observations from the Moon at very low frequencies Radio instrument technology demonstration for future lunar observatory and interferometry Radio receiver design for low‐frequency observation