Queqiao has some other cool tricks up its robotic sleeves. Marc Klein Wolt of Radboud University and project leader for the Netherlands-China Low-Frequency Explorer (NCLE), says the instrument will be switched on after the nominal 3-month lifetime of Yutu-2, in preparation to make unprecedented low-frequency radio observations of the solar system and potentially pick up signals from the cosmic dark ages. Like the Low Frequency Spectrometer (LFS) on Chang’e-4, NCLE consists of three 5-meter-long booms.

The relay sat is also carrying a 170-millimeter large-aperture laser angle reflector, which is a test instrument for carrying out laser ranging measurements and likely a precursor to a retroreflector for a future Chang’e landing mission.

There’s the possibility that Queqiao will have fuel enough to assist future missions, as the current outline for the planned Chang’e-7 mission to the lunar south pole in the early 2020s requires such a craft. If not, one suggestion for an extended mission would see Queqiao head to other Earth-Moon Lagrange points to confirm if the areas of stable orbits host small bodies, or ‘Trojans’, just as similar libration points in the Jupiter system do.

The Queqiao retroflector will be used to test ranging ability of the 1.2-metre telescope laser ranging system at the Yunnan Observatory at Kunming, under the Chinese Academy of Sciences, and the experiment could take place next month, says Li Yuqiang from Yunnan Observatory. The laser corner retro-reflector will receive laser light from an Earth station and reflect the light back to Earth. Yunnan Observatory successfully used the telescope laser ranging system to bounce light off a retroreflector placed on the Moon during NASA's Apollo 15 crewed lunar mission early last year.