# First results from the TUS orbital detector in the extensive air shower mode

## TL;DR

The TUS satellite, as the first space-based detector for ultra-high-energy cosmic rays, has collected atmospheric ultraviolet data, revealing diverse emissions and laying groundwork for future space observatories despite not conclusively detecting cosmic rays yet.

## Contribution

This paper presents the first operational results of the TUS orbital detector, testing space-based detection techniques for extensive air showers caused by extreme energy cosmic rays.

## Key findings

- Rich diversity of atmospheric ultraviolet emissions observed.
- No conclusive detection of ultra-high-energy cosmic rays yet.
- Data aids development of future orbital cosmic ray detectors.

## Abstract

TUS (Tracking Ultraviolet Set-up), the first orbital detector of extreme energy cosmic rays (EECRs), those with energies above 50 EeV, was launched into orbit on April 28, 2016, as a part of the Lomonosov satellite scientific payload. The main aim of the mission is to test a technique of registering fluorescent and Cherenkov radiation of extensive air showers generated by EECRs in the atmosphere with a space telescope. We present preliminary results of its operation in a mode dedicated to registering extensive air showers in the period from August 16, 2016, to November 4, 2016. No EECRs have been conclusively identified in the data yet, but the diversity of ultraviolet emission in the atmosphere was found to be unexpectedly rich. We discuss typical examples of data obtained with TUS and their possible origin. The data is important for obtaining more accurate estimates of the nocturnal ultraviolet glow of the atmosphere, necessary for successful development of more advanced orbital EECR detectors including those of the KLYPVE (K-EUSO) and JEM-EUSO missions.