Leonard David's INSIDE OUTER SPACE

Recent pass of China’s Tiangong-1as recorded by sky watching satellite tracker.
Credit: Thomas Dorman

Sky watchers are on the lookout for China’s Tiangong-1 space lab – and the seeing is good.

Tiangong-1 (“Heavenly Palace”) was hurled into Earth orbit in late September 2011. It was used for six successive rendezvous and dockings with spacecraft, Shenzhou-8 (uncrewed), Shenzhou-9 (piloted) and Shenzhou-10 (piloted) as part of China’s human space exploration activities.

Reentry prediction

At launch, the vehicle weighed 18,740 pounds (8,500 kilograms).

But in March of 2016, the space lab ceased functioning.

Docking of China’s Shenzhou 10 spacecraft with the Tiangong-1 space station June 13, 2013.
Credit: CCTV

Tiangong-1 is now predicted to reenter in late January 2018 ± 1 month.

This forecast was performed by The Aerospace Corporation on October 31 of this year. “It is unlikely that this is a controlled reentry. Although not declared officially, it is suspected that control of Tiangong-1 was lost and will not be regained before reentry,” according to The Aerospace Corporation’s Center for Orbital and Reentry Debris Studies (CORDS).

Based on Tiangong-1’s inclination, the lab will reenter somewhere between 43° North and 43° South latitudes.

Credit: Center for Orbital and Reentry Debris Studies (CORDS).

Slow roll

Ground viewing of the Chinese space lab, along with an analysis of images, suggests that the vehicle shows no sign of tumbling, but is apparently in a slow roll.

By not tumbling before nose-diving into the atmosphere, it’s possible that the multi-ton facility might not break up as much during the fiery fall. If that’s the case, it potentially increases the number of fragments that could reach Earth’s surface.

Leftovers

As for leftovers, the CORDS website states that “it is highly unlikely that debris from this reentry will strike any person or significantly damage any property,” adding: “potentially, there may be a highly toxic and corrosive substance called hydrazine on board the spacecraft that could survive reentry. For your safety, do not touch any debris you may find on the ground nor inhale vapors it may emit.”

The Aerospace Corporation adds that it will perform a person and property risk calculation for the Tiangong-1 reentry a few weeks prior to the event.

International campaign

Experts at the European Space Agency will host an international campaign to monitor the reentry of the Tiangong-1, conducted by the Inter Agency Space Debris Coordination Committee (IADC).

Artist’s concept of the Tiangong-1 in Earth orbit.
Credit: CMSA

IADC comprises space debris and other experts from 13 space agencies/organizations, including NASA, ESA, European national space agencies, JAXA, ISRO, KARI, Roscosmos, as well as the China National Space Administration.

IADC members intend to use the fall of Tiangong-1 to conduct their annual reentry test campaign, during which participants will pool their predictions of the time window, as well as their respective tracking datasets obtained from radar and other sources.

The Main Control Room at ESA’s European Space Operations Center, Darmstadt, Germany.
Credit: ESA/P. Shlyaev, CC BY-SA 3.0 IGO

The aim is to cross-verify, cross-analyze and improve the prediction accuracy for all members.

ESA will serve as host and administrator for the campaign, as it has done for the twenty previous IADC test campaigns since 1998.

Geographic footprint

Holger Krag, Head of ESA’s Space Debris Office, explains that China’s space lab reentry corridor already excludes the possibility that any fragments will fall over any spot further north than 43ºN or further south than 43ºS.

“This means that reentry may take place over any spot on Earth between these latitudes, which includes several European countries, for example,” Krag says.

“The date, time and geographic footprint of the reentry can only be predicted with large uncertainties,” Krag adds. “Even shortly before reentry, only a very large time and geographical window can be estimated.”

Owing to the station’s mass and construction materials, there is a possibility that some portions of Tiangong-1 will survive and reach the surface, according to an ESA statement.

For more information, go to my earlier Space.com story:

China’s Fall Guy: Tiangong-1 Space Lab to Crash in Early 2018

https://www.space.com/38573-china-space-lab-tiangong-1-re-entry-2018.html