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This paper presents a simple slit-mask-based sensing scheme that can be applied to a robust piston error sensor for segmented optical systems, even in space. Utilizing crossed fringes generated from multiple double-slit pairs, the sensor simultaneously detects multiple points in a segmented optical system in one shot. The experiments tested six pistons of a single-ring segmented mirror. The results showed measurement stability better than 15 nm in the range of 0–5 µm and absolute accuracy of λ / 20 . The theoretical perspective of applicability for larger piston measurement and N-ring segmented systems is also discussed, with simulation results for a two-ring system presented.

In space cryogenic missions, the thermophysical properties of materials must be studied and measured to establish a highly reliable cooling chain. An Al-alloy is a primary material in cryogenic thermal structural designs and is particularly used for providing high thermal conductance of thermal shields and thermal straps. We measured low-temperature properties (the thermal conductivity and the electrical resistivity) of several Al-alloys and found that A6063 had a lower thermal conductivity than that reported previously. We also found that the Al-alloy ST-60, which has equivalent thermal conductivity as pure aluminum, has higher thermal conductivity than A6061 and A6063, and the material is a good candidate for the space cryogenic design at the temperature range between 4K and 300K. These results are critical for the thermal study of upcoming next-generation space astronomy missions, such as LiteBIRD, SPICA and ATHENA.