Netherlands-China Low-Frequency Explorer shown in orbit at Earth-Moon L2 point.The Netherlands-China Low-Frequency Explorer (NCLE), is a low-frequency radio experiment for the Chinese Chang'e 4 mission that will go in a Lissajous orbit around the Earth-Moon L2 point in 2018. NCLE is considered a pathfinder mission for a future low-frequency space-based or moon-based radio interferometer which has the detection and tomography of the 21-cm Hydrogen line emission from the Dark Ages period as the principle science objective. Low-frequency radio astronomy, i.e. below ~30 MHz, can only be done well from space due to the cut-off in the Earth's ionosphere, the man-made RFI and the AKR and QTN noise that make sensitive measurement from ground-based facilities impossible.

At the Earth-Moon L2 point NCLE will be outside the Earth's ionosphere and relatively far away from terrestrial interference, which, however, will still be detectable. As the Earth will always be in sight we can measure and quantify this emission for the first time since 50 years and with unprecedented quality. This will allow us not only to study the radio- and plasma physics of the earth-moon system, but also to explore mitigation and calibration techniques for exploring radio emission from the early universe and compare it with measurements made in true lunar far-side locations made by future (Chinese) Lunar Lander missions.