Mechanical design and structural analysis for LiteBIRD low-frequency telescope and payload module

LiteBIRD is a spacecraft to observe the polarization signal of the cosmic microwave background radiation (CMB). In the development of its payload module, it is important to design the mechanical structures with enough rigidity to withstand the launch environment while providing enough thermal insulation to cool the telescopes down to 5 K. We need to reduce the mass of the 5-K structure, which consists of three telescopes, the low-frequency telescope (LFT) led by JAXA and the mid-frequency and high-frequency telescopes (MFT and HFT) led by CNES. In this paper, we report the mechanical design of the LFT and the structural analysis using Nastran. We made a structural mathematical model of the LFT and performed modal and quasi-static analyses. We successfully reduced the LFT mass while keeping the natural resonance frequency higher than requirements. Additionally, we report the mechanical design and the current status of the structural analysis for the payload module.