Is China's Tiangong-1 space station really hurtling toward Earth like an out of control fireball?

The stability of China’s first space station Tiangong-1 is under question. Chinese authorities have made no public statements to declare the exact time the eight-ton uncrewed spacecraft will come back to Earth, leading to speculation that it may end up in a dangerous uncontrolled fall.

Since its launch in 2011, Tiangong-1 has conducted six rendezvous and docking missions with three Shenzhou spacecrafts. It exceeded its planned two-year operational lifespan, and entered its extended application phasein 2013.

Amateur satellite tracker Thomas Dorman worries that China has lost control of Tiangong-1 after Xinhuareported in March that the data-gathering activities of the spacecraft had come to an end.

Dorman has been tracking the movements of Tiangong-1 since its launch and backs his concern with images taken from the ground suggesting that the space station’s solar panels are no longer oriented towards the sun,Space.com reports. He says that if he is right, “China will wait until the last minute to let the world know it has a problem with their space station."

Dean Cheng -- senior research fellow at an Asian Studies center of a Washington-based think tank -- is quoted by Space.com as agreeing with Dorman’s speculations.

Cheng said that he was surprised that Chinese authorities have not declared the exact time the space station will come back to earth, even though its operation life seems to be over, speculating, “that would seem to suggest that it's not being deorbited under control.”

Another expert is much more optimistic about China's space program. T.S. Kelso -- senior research astrodynamicist at the Center for Space Standards & Innovation -- gave an alternative reading of Tiangong-1’s condition, saying that the spacecraft is dormant but stable.

"So that might be why the Chinese aren't responding … they probably don't understand why they would need to," Kelso told Space.com.

In an article unrelated to Tiangong-1, Sebastian Willems, a researcher at the German space agency, is quoted by the BBC as saying that “typically one big object re-enters the Earth’s atmosphere every three-to-four days.”

Mission controllers plan how the satellites return to Earth by using their remaining fuel to push them on controlled trajectories to burn up over remote areas of ocean. “It is the unplanned re-entries of dead spacecraft that are of greater concern,” said Willems. He adds that the recent unplanned re-entry of NASA’s six-ton Upper Atmosphere Research Satellite (UARS) in 2011 had a 1 in 2,500 chance of causing a casualty.

“It could be a real bad day if pieces of this came down in a populated area … but odds are, it will land in the ocean or in an unpopulated area,” Dorman himself said.

While the Independent reported Space.com’s speculations under the headline “China space station Tiangong-1 could secretly be hurtling towards Earth, astronomers say”, web users in the comment section seem to be untroubled by the risk of the rumored uncontrolled fall. Here are some of their comments:

“So it's a satellite and not a space station, and it's in free-fall (as are all the other thousands of satellites around the earth) not hurtling to Earth. Plus most of it is going to burn up in the atmosphere, and whatever is left, if any, is going to be molten metal that is almost likely to land in the ocean or an uninhabited part of the earth. Can you get a more alarmist headline?” wrote Mazin.

“What are the odds that it ‘accidentally’ crashes down into the South China Sea creating a metallicisland that the Chinese claim as sovereign territory?” wrote rawhead_wrecker.Judging from our own archive, whole pieces of debris from rocket launches seem to be a more substantial danger.

Bron: http://shanghaiist.com/2016/07/13/tiangong-1-falling.php 

satellieten live volgen: http://www.space.com/32054-satellite-tracker.html 
Meer info op: http://www.space.com/33140-china-tiangong-1-space-lab-falling-to-earth.html  | Gewijzigd: 1 februari 2017, 10:11 uur, door Joyce.s