Mir
The space station Mir (Russian for peace), a product of the Russian Space Agency, was a research facility in orbit around Earth in the late 20th century.
Sometime before 2032, it disintegrated. That year, when Rose Kumagawa claimed she saw a UFO over the Gulf of Mexico, Lieutenant John Kelly told her that it probably was a meteor or a piece of Mir. Kelly recalled this when he was trapped inside a spatial anomaly, mentioning that he regretted giving her a hard time about the incident. (VOY: "One Small Step")
The actual operational life of this station, from February 1986 to March 2001, was noted in the Star Trek Encyclopedia, 4th ed., vol. 2, p. 44. It was constructed in orbit and used by astronauts from many nations.
Mir's disintegration actually took place in 2001, two years after this episode aired.