Large-format and compact stressed Ge:Ga array for the ASTRO-F (IRIS) mission Original Research Article

We describe the development of a stressed Ge:Ga array detector with a large pixel format but a compact mechanical structure. The detector will be deployed in IRIS, a Japanese satellite to be launched in 2004, which will conduct an all-sky, far-infrared survey as well as spectroscopic observations of specific objects. The array has a 5 × 15 pixel format. Three of the five rows are for the 100 – 200 μm band, and the other two are for the 150 – 200 μm band. In the focal plane of the IRIS telescope, each pixel corresponds to a field of view of 50″ × 50″. A uniaxial mechanical stress is applied to the detector chips in each row using a single stressing mechanism. This results in a compact focal-plane array. Light pipes with entrance apertures of 0.9 × 0.9 mm size are distributed with a pitch of 1 mm. A charge-integrating amplifier (CIA) circuit is used as the readout. Bare-chip amplifiers and multiplexers are placed behind the Ge:Ga chips and are cooled to 1.8 K. The entire system, including chips and readouts, weighs 300 grams. We have thus succeeded in building a compact array detector suitable for a satellite payload.