Ultra-lightweight and hyper-thin rollable primary mirror for space telescopes

摘要

The aperture of monolithic space telescope primary mirrors placed on orbit is limited to payload faring diameters, the largest being about 4-meters. This requires a novel stowage approach for monoliths larger than 4-meters. Very large aperture telescopes, 50 to 100-meter diameters, planned for deployment in the next 10 to 20 years will aso require very large mirror segments in an effort to manage the phasing of the entire surface. The larger the mirror panels the fewer that will be required for such apertures. If the mirrors can be made thin enough to be deformed into a cylinder or undeformed but closely nested, enough surface area can be placed on orbit to facilitate large aperture telescope mirrors. 8-meter monolithic mirrors can be rolled into a 2.5-meter diameter cylinder with the secondary support structure stowed in the cylinder to maimize the payload faring volume. Hyper-thin mirrors can be closely nested in order to maimize volume as well. Presented is a design and engineering model of a 0.9-meter diameter hyper-thin, ultra-lightweight spherical composite mirror and methods, which led to the fabrication of the mirror. The optical composite mirror has the ability to be rolled into a cylinder and then deployed to yield an actively controleld monolithic space telescope primary mirror. The engineering concerns associated with applying such stresses to the mirror include creating a laminated mirror substrate with the proper in-plane properties and controlling residuals or hysteresis effects on the optical surface after cycles of rolling an unrolling. We present optical data, which suggests the ability of such a mirror to be manufactured to nearly optical figure tolerance.