The DART cylindrical, infrared, 1 meter membrane reflector

摘要

The Dual Anamorphic Reflector Telescope (DART) is an architecture for large aperture space telescopes that enables the use of membranes. A membrane can be readily shaped in one direction of curvature using a combi- nation of boundary control and tensioning, yielding a cylindrical reflector. Two cylindrical reflectors (orthogonal and confocal) comprise the 'primary mirror' of the telescope system. The aperture is completely unobstructed and ideal for infrared and high contrast observations. The DART high precision testbed researches fabrication, assembly, adjustment and characterization of 1 meter cylindrical membrane reflectors made of copper foil or kapton. We have implemented two metrology instruments: a non-contacting, scanning profilometer and an infrared interferometer. The profilometer is a laser confocal displacement measuring unit on an XYZ scanning stage. The infrared interferometer uses a cylindrical null lens that tests a subaperture of the membrane at center of curvature. Current surface figure achieved is 25 μm rms over a 50 cm diameter aperture.