Tiangong-1 Reentry

The world watched and waited as the Chinese space station Tiangong-1 hurtled towards a fiery reentry. Please visit our media kit page for background information.

This prediction was performed by The Aerospace Corporation on 2018 April 1.

(Click on image to view full-size image.)

Dotted lines indicate dates of probable orbital maneuvers.

On 2016 March 21, an official Chinese statement declared that telemetry services with Tiangong-1 had ceased. Based on The Aerospace Corporations analysis of Two-Line Element set data from the JSpOC, the last orbitaladjustment for Tiangong-1 was made in December 2015. Likewise, amateur satellite trackershave been tracking Tiangong-1 and claimit has been orbiting uncontrolled since at least June 2016. On 2016September 14, China madean official statement that they predict Tiangong-1 will reenter the atmosphere in the latter half of 2017. China later updated its prediction via an announcement to the UNs Committee on Peaceful Uses of Outer Spaceon December 8, 2017. It was not mentioned whether the reentry was to betargeted or remain uncontrolled.

It is a well known scientific principle thatany measurement or prediction will always have an associated uncertainty. In the case of most reentering objects, the uncertainty associated with predicting reentry location is extremely large and precludes an accurate location prediction until shortly before the reentry has occured.In general, it is much easier to predict an accurate reentry time rather than an accurate reentry location. Based on Tiangong-1s inclination, however, we can confidently say that this object will reenter somewhere between 43 North and43 South latitudes.

Due to the uncertainties involved it is very difficult to predict the exact timing of a space objects reentry. There are several sources of uncertainty which include: 1) significant variation in the density of the upper layers of the atmosphere, 2) significant uncertainties in the orientation of the space craft over time, uncertainties in some physical properties of the spacecraft such as the exact mass and material composition, and 3) uncertainties in the exact location and speed of the space station. When aggregated, these factors translate into a reentry timing uncertainty that is roughly 20% of the time to go (the time between the date of the prediction and the predicted date of reentry).

It is highly unlikely that debris from this reentry will strike any person or significantly damage any property.The only known case of space debris striking a person is Ms.Lottie Williams of Tulsa, Oklahoma who was struck by a small piece of space debris in 1996 but was not harmed in any significant way.

As reentry gets closer, we are able to narrow possible reentry locations to a collection of specific ground tracks instead of broad regions of the globe. As the reentry time gets closer, the number of ground tracks will diminish until we are left with only one, and after that with only a portion of a single ground track. Areas not within the ground tracks are clear. The exact statistical likelihood of you or your property being struck by reentering debris is constantly changing. Potential reentry points and whether the final ground track is over inhabited or uninhabited areas will determine the risk to a specific location. Even so, the likelihood of any one person (i.e. YOU) being struck by debris is still far less than winning the Powerball Jackpot.

It is unlikelythat 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.

No, no astronauts are currently on board Tiangong-1. The last manned mission departed from Tiangong-1 in June 2013.

It may be possible to see Tiangong-1 reentering depending on your 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. Visiblyincandescent objectsfrom 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.

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 Earths surface. Some examplesof reentries can be found here: video 1, video 2.

Potentially,there may be a highly toxic and corrosive substance calledhydrazine 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.

Yes. Contact CORDS at http://www.aerospace.org/cords/contacting-cords/ Please report your location and time of the sighting, a description of what you saw, and provide any images or videos you may have captured of the reentry.

No. The largest object to reenter is the Mir space station at 120,000 kg which reentered on 2001 March 23. In comparison, Tiangong-1 is only 8,500 kg. For further space debris reentry information, consult the table onthis page.

In the history of spaceflight, no known person has ever been harmed by reentering space debris. Only one person has ever been recorded as being hit by a piece of space debris and, fortunately, she was not injured.

Tiangong-1 FAQ

Tiangong-1 Reentry Update

Tiangong-1 Captured via Telescope

Reentry Test Campaign Announcement

Basic Tiangong-1 background info

Official statement regarding Tiangong-1 telemetry ceasing

Official statement regarding Tiangong-1 reentry

Amateur satellite trackers claim Tiangong-1 likely uncontrolled

Controlled vs. uncontrolled reentries

General reentry info

Newsweek

Wired

New York Times

Reuters: Tiangong-1 is not out of control

Chinas Manned Space Program

See the rest here:

Tiangong-1 Reentry | The Aerospace Corporation