The 4K focal plane unit for SPICA's SAFARI far infrared instrument

Abstract

SPICA provided the next step in mid- and far-infrared astronomical research and was a candidate of ESA's fifth medium class Cosmic Vision mission. SAFARI is one of the spectroscopic instruments on board SPICA. The Focal Plane Unit (FPU) design and analysis represent a challenge both from the mechanical and thermal point of view, as the instrument is working at cryogenic temperatures between 4.8K and 0.05K. Being a large instrument, with a current best estimate of 148,7kg of mass, its design will have to be optimized to fit within the mission´s mass and volume budget. The FPU will also have to be designed for its modularity and accessibility due to the large number of subsystems that SAFARI had to accommodate, highlighting Fourier Transform Spectrometer Mechanism (FTSM) and the three grating-based point source spectrometer modules (GM) which operates at 1.7K in the FPU, the latter representing 60% of the total mass of the instrument