The Chang’e-4 mission from China has a lot of firsts in the field of space exploration. Since it launched in December 2018 and successfully deployed the lander and the Yutu 2 rover, China became the first country to achieve a soft landing on the far side of the Moon. Coupled with this success, it has announced the first ever germination of plants outside the safe confines of Earth.
Not resting on its laurels, Chang’e-4 has entered the next phase of its mission by commencing operations of a radio telescope. The Netherlands-China Low Frequency Explorer (NCLE), which was mounted on the Queqiao communications satellite which consists of three 5 meter (16.4 ft) long monopole antennae tuned to be sensitive of frequencies between 80 kHz and 80 MHz, started operations one year after orbiting the Moon.
This radio observatory is a product of the collaboration between Netherlands Institute for Radio Astronomy (ASTRON) and the Chinese National Space Agency (CNSA). ASTRON currently operates one of the largest radio telescopes in the world, the Westerbork Synthesis Radio Telescope (WSRT), an inherent part of the European Very Long Baseline Interferometry Network (EVN).
The NCLE has chosen the far side of the Moon as an ideal spot for conducting their radio experiments as it is shielded from the Tellurian radio waves. Since it cannot communicate directly with Earth, Queqiao acts as a liaison between the observatory and Earth.
The NCLE is built exclusively to detect radio waves in the 21 cm (Hydrogen Line) emission range which correlates with the earliest history of our universe, known as the dark ages, which could answer some outstanding questions about this hitherto unknown period.
These include questions about the nature of dark matter, dark energy including the provenance of the earliest stars and galaxies.
As the primary goal of the Chang’e-4 mission bore fruition, the China National Space Agency (CNSA) has entered the next phase, which is to conduct radio experiments on the far side of the Moon.
Marc Klein Wolt, Managing Director of the Radboud Radio Lab, who heads the Dutch team succinctly expressed that they now have the opportunity to perform observations uninterrupted during the fourteen day long night at the far side of the Moon.
As always, unfolding of the antennae is the most crucial part, directly determining the future of the mission and since that functioned as seamlessly as possible, this could be a stepping stone for future radio instruments in space. Radio astronomers around the world are awaiting the NCLE’s first radio measurements.
Professor Heino Falcke, the chair of astrophysics and radio astronomy at the Radboud University, also the scientific leader of the joint collaboration extolled his team’s contribution and dedication to the project and was proud of the fact that there’s a radio instrument of Dutch origin in space.
The deployment of the antennae happened after a yearlong wait and as a result had some ramifications when the antennae unfurled; the process became labored and sluggish as time went on and hence they decided to collect data from the partially unfurled antennae, hoping to deploy the rest later on.
At its current sensitivity, the partially unfurled antennae can detect signals from 800 million years after the Big Bang, a period believed to be when the first stars and galaxies were forming.