Monitoring the orbital decay of the Chinese space station Tiangong-1 from the loss of control until the re-entry into the Earth's atmosphere

Launched in September 2011, the first Chinese space station Tiangong-1 was originally planned to be deorbited with a controlled re-entry at the end of its operational life. However, due to a fatal on-board failure that occurred in March 2016, it was irremediably doomed to an uncontrolled decay. The latter was regularly monitored at ISTI-CNR, which also joined an international re-entry campaign, starting a couple of months before the final decay, on 2 April 2018, apart from providing support to the Italian Space Agency for the National Department of Civil Protection. In spite of numerous challenges encountered during the campaign, due to the complex dynamics of the re-entering object, due to the lack of information on its structure and fragmentation process, and due to the distinctive characteristics of the space environment, often not properly represented by the available semi-empirical thermosphere density models, reasonable and conservative solutions were devised and applied, providing a valuable support to plan, at national level, the appropriate measures to mitigate the potential risk to airspace and on the ground due to falling debris from this uncontrolled re-entry.