We present a conceptual design for a cryogenic optical mechanism for the SAFARI instrument. SAFARI is a long
wavelength (34-210 micron) Imaging Fourier Transform Spectrometer (FTS) to fly as an ESA instrument on the JAXA
SPICA mission projected to launch in 2021. SPICA is a large 3m class space telescope which will have an operating
temperature of less than 7K. The SAFARI shutter is a single point of failure flight mechanism designed to operate in
space at a temperature of 4K which meets redundancy and reliability requirements of this challenging mission. The
conceptual design is part of a phase A study led by ETH Institute for Astronomy and conducted by RUAG Space AG.