China's Tiangong-1 space station made news after Chinese authorities revealed it would fall back to Earth. In April, the China Manned Space Engineering Office announced that the experimental space laboratory has hurtled toward Earth albeit most of it burned up during re-entry.
Strange Maneuver
Now, the doomed space station's successor, Tiangong-2, has also been observed to display strange behaviors. On June 13, Tiangong-2 unexpectedly dropped from its normal orbit of 242 miles to 183 miles. Unlike its predecessor, however, the spacecraft is not falling back to Earth, as it later returned to its original position.
Jonathan McDowell, an astrophysicist from the Harvard-Smithsonian Center for Astrophysics, revealed that the spacecraft returned to its normal orbit after spending 10 days in the lower orbit.
The unexplained maneuver led to speculations that China may be about to decommission the spacecraft in a more controlled manner than Tiangong-1.
McDowell said that it is possible that the lowering of Tiangong-2's orbit marks the first step in safely disposing it. Tiangong-1 slipped out of control but fortunately hurtled back to Earth harmlessly.
McDowell also thinks that that the space station's orbit was likely lowered through two burns early on June 13 and then returned to higher orbit through another two burns.
Phil Clark, who has been observing China's space activities, has been tracking the orbit of Tiangong-2 since it was launched. He noted of a recent relative absence of burns to raise the station's orbit, prior to the last week's activity.
"In part China doesn't want a repeat of Tiangong-1 going rogue," Clark said.
Tianhe 1 And Tiangong-2
It remains unclear what is the reason behind the strange maneuver. Nearly 900 pounds of propellant, however, is still on the space station, which supports the idea that China is conducting safe deorbit tests.
"For this specific propulsion system, maybe they'd like additional on orbit test data - esp to qualify the longevity of the system (measure performance after 2 years on orbit)," McDowell tweeted. "Maybe planning to use same propulsion design on Tianhe."
Tianhe 1, is the core module of the Tiangong-3 space station, China's first multi-module space outpost that the country eyes to complete by the year 2022 with three major module in total. China anticipates to launch the first module around 2020.
Tiangong-2 was launched in 2016 and has served as a test-bed for technologies that China wants to integrate into Tianhe. In 2016, two Chinese astronauts spent 30 days in orbit aboard the spacecraft, in what is currently China's longest human spaceflight mission.
