Preliminary design of the InfraRed Telescope instrument for the ESA THESEUS mission

This paper presents the preliminary structural design of the InfraRed Telescope, a large aperture space instrument onboard the THESEUS satellite. The mission is candidate to be selected for the ESA Cosmic Vision program and aims to enhance the knowledge of high-energy transient phenomena by observing the footprints left by early universe stars within their life cycle. The feasibility design process involved identifying the baseline mission requirements to develop a structural design capable of meeting these constraints while ensuring a large maturity margin. This was achieved relying also on the careful selection of materials with strong space heritage, ensuring the designed components performance, robustness and reliability in the demanding space environment foreseen for the mission. A conceptual study of the telescope assembly was divided into three structural subsystems, which were developed in parallel adopting a finite element analysesbased design approach. The subsystems were then integrated to assess the compliance with the design requirements on a complete finite element model of the InfraRed Telescope. This preliminary study enabled the design of a robust structural proposal for the instrument, fulfilling the design requirements regarding the mission vibrational environment and overcoming the loads expected during the launch and orbital insertion phases of THESEUS. This design will be further refined by incorporating higher-level requirements into the development loop, aiming to finalize the telescope study and complete the thermo-mechanical design activities.