By 
October 24th, 2017
Artist’s concept of the Tiangong-1 in Earth orbit.
Credit: CMSA
China’s Tiangong-1 space lab is headed for an uncontrolled and destructive nose-dive into Earth’s atmosphere early next year.
Exactly when and where on Earth the multi-ton discarded craft will make its plunge cannot now be predicted. What is known is that the vehicle will reenter somewhere between 42° North and 42° South latitude.
Tiangong-1 (“Heavenly Palace”) was rocketed 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. The vehicle weighed 18,740 pounds (8,500 kilograms) at launch.
Back in March of 2016, the space lab ceased functioning and to date the spacecraft has maintained its structural integrity. In length, the vehicle is 34 feet (10.5 meters) and sports a diameter of 11 feet (3.4 meters). The lab has two solar panels (approximately 23 feet (7 meters) by 10 feet (3 meters).
Credit: T.S. Kelso
Dropping in altitude
A check of orbital data shows that Tiangong-1 has been slowly dropping from its roughly 360 kilometer altitude at the beginning of 2017 to roughly 310 kilometers at present, explains T.S. Kelso, a senior research astrodynamicist at the Center for Space Standards & Innovation (CSSI), a research arm of Analytical Graphics.
Using two-line element (TLE) data, a format for distributing orbital element data of spacecraft, “we would expect to see reentry occur somewhere around the last week of March 2018,” Kelso told Inside Outer Space.
Notification
Earlier this year, the United Nations Office for Outer Space Affairs (UNOOSA) reissued a notification by China on the future uncontrolled re-entry of the country’s Tiangong-1 space lab.
“The probability of endangering and causing damage to aviation and ground activities is very low,” the notification states.
The notice advises that China attaches great importance to the re-entry of Tiangong-1 and will take the following measures in terms of monitoring its fall and providing public information:
— China will enhance monitoring and forecasting and make strict arrangements to track and closely keep an eye on Tiangong-1 and will publish a timely forecast of its re-entry
— China will make use of the international joint monitoring information under the framework of the Inter-Agency Space Debris Coordination Committee in order to be better informed about the descent of Tiangong-1.
— China will improve the information reporting mechanism. Dynamic orbital status and other information relating to Tiangong-1 will be posted on the website of the China Manned Space Agency (www.cmse.gov.cn) in both Chinese and English. In addition, timely information about important milestones and events during the orbital decay phases will be released through the news media.
— As to the final forecast of the time and region of re-entry, China will issue the relevant information and early warning in a timely manner and bring it to the attention of the United Nations Office for Outer Space Affairs and the Secretary-General of the United Nations by means of “note verbale” through diplomatic channels.
Credit: CORDS/The Aerospace Corporation
Leftovers
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.
A prediction performed by The Aerospace Corporation on October 18, 2017 shows Tiangong-1 reentering in late January 2018 ± 1 month.
As for lingering 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 will perform a person and property risk calculation for the Tiangong-1 reentry a few weeks prior to the event.
Credit: CORDS/The Aerospace Corporation
Reentry viewing
According to CORDS, it may be possible to see Tiangong-1 reentering depending on the viewer’s location, the time of day, and visibility during reentry which will not be known until a few days prior to the event. A more detailed predicted reentry region will be provided a few days prior to the reentry time frame. Visibly incandescent objects from this reentry will likely last tens of seconds (up to a minute or more) in contrast with the vast majority of natural meteors which last mere seconds.
CORDS also notes that, depending on the time of day and cloud visibility, the reentry may appear as multiple bright streaks moving across the sky in the same direction. Due to the relatively large size of the object, it is expected that there will be many pieces reentering together, some of which may survive reentry and land on the Earth’s surface.
Resources
Check out this video taken by the European Space Agency (ESA) from an observation aircraft showing the ESA Automated Transfer Vehicle (ATV-1) spacecraft reentering over the Pacific Ocean after completing its ISS resupply mission. Go to:
For an older story of mine, back in June 2016, China’s “Heavenly Palace” – Headed for a Hellish Demise?, go to:
https://www.leonarddavid.com/chinas-heavenly-palace-headed-for-a-hellish-demise/
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