What’s Going on with Tiangong-2?

UPDATE July 13th: CMSEO announced Tiangong-2 is slated to re-enter on July 19th.

Beijing has been silent about the Tiangong-2 space station, which is supposed to be reentering the atmosphere this month. The China Manned Space Engineering Office (CMSEO) announced the controlled reentry of Tiangong-2 in July 2019. The decision was reportedly made on September 20th, but it was likely made much earlier considering CMSEO performed orbit-lowering maneuver in June that lowered the station’s 383 kilometers down to 295 kilometers.

However, there have been no updates as to the status of Tiangong-2 except for one on January 16th:

The China Manned Space Engineering Office revealed on January 15 that the gamma-ray polarization detector installed in the Tiangong-2 Space Laboratory has completed the high-precision polarization detection of gamma-ray burst instantaneous radiation. The relevant results were published online on January 14. In the international academic journal Nature and Astronomy.

The scientific results published this time are the best polarization observations since the discovery of the Gamma storm in the 1960s, which is conducive to a better understanding of the formation of black holes and the generation of extreme relativistic jets. The study of basic scientific issues in extreme physical environments and conditions in the universe plays an important role.

Launched in 2016, Tiangong No. 2 has carried out 14 space science and application tasks that reflect the international scientific frontier and high-tech development direction, including the world’s first large-area, large-field, high-precision gamma-ray storm jointly developed by China and Europe. Polarization detector has become one of the typical international cooperation projects for manned spaceflight projects in China.

During the orbital operation, the gamma-ray polarization detector performs well and is calibrated accurately, completing all on-orbit observation tasks. A total of 55 gamma-ray bursts were detected, and high-precision polarization measurements were performed on five of the gamma-ray bursts. This is the largest high-precision gamma-ray polarization measurement sample in the world. It is found that the average polarization degree during the gamma-ray burst is low, about 10%, and the evolution of the polarization angle of the gamma-ray burst in a single pulse is found. These observations indicate that the internal evolution of the extreme relativistic jets that produce gamma rays may result in rapid changes in the polarization angle, resulting in a lower average polarization of the observed gamma ray bursts.

These scientific discoveries also raise new scientific issues. Therefore, scientists from Switzerland, Germany, Poland and other countries have formed an expanded international cooperation team for gamma-ray polarization detectors. Sweden, Japan and other countries have also proposed cooperation intentions and contributions. The international cooperation team has officially submitted the “Gamma Polarization Probe No. 2” proposal for the follow-up experiment of the China Space Station, which is expected to make a key contribution to the final resolution of major scientific issues such as black hole formation and extreme relativistic jet generation.

There have also been no updates to UNOSSA and the Register of Space Objects, although there is a submission, ST/SG/SER.E/856, being processed. It is unknown whether this relates to Tiangong-2.

Beijing’s silence on the status of the Tiangong-2 is curious considering the near public relations disaster with Tiangong-1’s reentry. That isn’t to say an update won’t be made perhaps a few days before it reenters, but it is still interesting there have been no public statements or filings regarding the impending reentry.

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