A search for extreme energy cosmic rays and nuclearites in TUS observations and a study of the relative exposure

TUS (Track Ultraviolet Setup) is the first orbital detector designed to check the possibility of recording Extreme-Energy Cosmic Rays (EECRs) events at E > 100 EeV by measuring the fluorescence signal of Extensive Air Showers (EAS) in the atmosphere. Funded by the Russian Space Agency ROSCOSMOS, TUS has operated as a part of the scientific payload of the Lomonosov satellite between April 2016 and November 2017. The collected data have been analyzed to search for EECRs and for possible strangelets (nuclearites) and determine their properties through comparison with simulated candidates obtained by means of the ESAF (EUSO Simulation and Analysis Framework) software. No clear candidate has been identified. A study of the aperture and exposure acquired by TUS in EECR and nuclearite modes has been conducted. This study is extremely important in view of the present and future space-based missions related to EECRs such as Mini-EUSO, K-EUSO and POEMMA.