On April 2, 2018 at 00:16 UTC, the Chinese “Tiangong-1” space station re-entered Earth’s atmosphere over the southern Pacific Ocean. The most of “Tiangong-1” was expected to burn up during re-entry. The mission control center in Beijing monitored the space station’s descent. The Russian 821st Main Space Intelligence Centre as well as United States Space Surveillance Network also monitored the space station’s descent.

The registered letter was sent from the Post office which situated not far from the Russian 821st Main Space Intelligence Centre. Total 56 such registered letters were sent at that day.