CHINA has brought its Tiangong-2 space-station closer to Earth’s upper-atmosphere, before boosting it back higher again.

The US military has observed that the Chinese space station has been deliberately ‘deorbited’ from a height of 380km to about 295km on June 13. But over the weekend, it has once again been returned to its safer, higher orbit.

Harvard-Smithsonian Center for Astrophysics astrophysicist Jonathan McDowell said on Twitter: “OK, now that’s weird … Wonder what that was about?”

Earlier, he had commented the lower orbit may mean Tiangong-2 was “probably about to be deorbited.”

Its sister space station — Tiangong-2 — went out-of-control in 2016, prompting widespread speculation as to whether or not it could rain deadly metal debris down on heavily populated centres. It eventually crashed-down in April this year without incident.

Tiangong-1 was launched in 2011. Tiangong-2 is much younger, having only been launched in September 2016.

Both were set in orbit to test human life support facilities, as well as docking and resupply mechanisms for its 20-ton modules. These are apparently templates for a modular Chinese space station due to be launched in the early 2020s.

Tiangong-2 is about 10.5m long and 3.4m wide. It weighs about 8.6 tons. In 2016, two astronauts stayed aboard for about 30 days. This is China’s longest stay in space so far.

The US Strategic Command’s Joint Force Space Component Command and the Joint Space Operations Centre highlighted Tiangong-2’s downward movement, which happened on June 13.

China itself, however, remains silent on the manoeuvre. Beijing state-run media initially denied there was any problem with Tiandong-1. Only later did it participate in the international discussion over the implications of its fate.

China is not permitted to participate in the International Space Station’s experiments. This has spurred it to begin construction of its own fully-operational orbital outpost, named Tianhe, in 2020. Weighing up to 100 tons, the station is expected to be operational by 2022 when two experiment modules are added to its core habitat facility.

Beijing says it hopes to maintain three crew on the station at any one time.

Its major feature will be a Hubble-like telescope, operating in close proximity to the space station. When the telescope needs repairs, refuelling or recalibrating, China hopes to dock it with the space station for the necessary work.