1-m Membrane Developed for Space Telescopes

Improvements to higher-resolution optical systems for space deployment are dependent upon the development of lighter weight and less expensive primary mirrors. Researchers from the US Air Force Academy in Colorado and L'Garde Inc. in Tustin, Calif., report the development and successful ground testing of a 1-m-diameter membrane mirror with an areal mass of 17 g/m².

Constructed with a series of Kevlar strings and tension adjusters attached to the back, the mirror can be deformed into a concave surface with 166 dimples. Although lightweight and easily unfurled, the extreme slopes of the mirror cause it to show a surface error of more than 15,000 waves upon illumination with collimated light. However, the researchers corrected this holographically, and successfully tested the telescope by imaging a 1951 Air Force resolution test target. They achieved a resolution of 90 line pairs per millimeter, with the theoretical resolution limit being 148 line pairs per millimeter. The work is described in the July issue of Optical Engineering.