Ultra-high energy cosmic ray detector TUS: preliminary results of the first year of measurements
TUS (Tracking Ultraviolet Set-up) is the first orbital detector of extreme energy cosmic rays. It was launched into orbit on April 28, 2016, as a part of the scientific payload of the Lomonosov satellite. The main aim of the mission is to test the technique of measuring UV fluorescent and Cherenkov radiation of extensive air showers (EAS) generated by primary cosmic rays with energies above ~50 EeV. The first year of operation has revealed an unexpectedly rich diversity of UV radiation. Among different types of registered events, we have identified those caused by thunderstorm activity and transient luminous events (TLEs), anthropogenic factors and by low-energy cosmic rays passing through the UV glass filters covering the focal plane. Three modes of operation aimed at studying TLEs and meteors were also tested. A search and analyses of EAS candidates is in progress. We report the preliminary results obtained during the first year of TUS operating in orbit in all modes of operation with a special attention to the EAS mode.