The Infra-Red Telescope on board the THESEUS mission

Abstract

The Infra-Red Telescope (IRT) on board THESEUS will play a key role in identifying and characterizing moderate to high redshift Gamma-Ray Bursts afterglows. The IRT enables the on board GRB autonomous redshift determination, thus allowing the ground based telescopes to be triggered on a redshift pre-selected sample and finally fulfilling the cosmological goals of the mission. The IRT will be composed by a primary mirror of 0.7 m of diameter coupled to a single camera in a Cassegrain design. It will work in the 0.7-1.8 mu m wavelength range, and will provide a 10×10 arc min imaging field of view with sub-arc second localization capabilities, and, at the same time, a 5×5 arc min field of view with moderate (R up to ∼500) spectroscopic capabilities. Its sensitivity, mainly limited by the satellite jitter, is adapted to detect all the GRBs, localized by the THESEUS SXI/XGIS instruments, and to acquire spectra for the majority of them.