  The TUS detector was the first space-based mission aimed for
ultra-high-energy cosmic ray (UHECR) measurements. The detector was designed to
register the fluorescent signal of extensive air showers (EAS) developing in
the night atmosphere of Earth in the UV range of 300-400 nm. TUS was launched
on board the Lomonosov satellite in April, 2016 and operated till December,
2017. Almost 90 thousand events were recorded during the mission, among them
lightning discharges, meteors, transient luminous events, polar lights and
anthropogenic signals. Some puzzling bright UV flashes in a clear sky far from
possible artificial sources were also registered. Besides this, a number of EAS
candidates were found in the TUS database. The majority of candidates analysed
so far were recorded above populated areas near airports or similar objects,
and the energy of the signals corresponds to at least 1 ZeV if they were
generated by an UHECR, which does not allow one to consider these events as
UHECRs. We briefly present the main results of the TUS experiment and discuss
its importance for the development of the future orbital missions.
