ISPI Mechanical Design
ISPI is side-looking so that it may be mounted on the 4-m simultaneously with Hydra II. The space envelope is constrained by the mirror cell above and Hydra below. The refractive optical system is enclosed in a cylindrical, straight-through design with a strong heritage from the facility IR camera CIRIM. Liquid cryogens are used for instrument cooling.
The design separates into two dewars with separate cryogen tanks which surround the optical path. The fore dewar has the entrance window, collimator, and filter wheel assemblies. The aft dewar holds the camera and detector assemblies. The cylindrical construction provides a very stiff assembly to meet flexure requirements. The diameter is 14 inches and the total length of the dewar assembly is 45 inches, the weight for the complete assembly is expected to be ~220lbs.
The filter wheels provide 16 positions including darks and opens. There is a single fixed Lyot stop. Alignment to the telescope is accomplished by adjustments at the telescope interface.
March 22, 2004