Replication as an alternative approach for large segmented telescopes

The next generation of optical/IR telescopes will require large numbers of co-phased segmented mirrors. Therefore, some form of replication technology is desirable to reduce costs. Electroforming has the advantage that it is a commercially developed technology for replication, and the technology has been widely used for making X-ray mirrors (e.g. XMM-Newton). Composite materials are appealing, since a great deal of development work as been done with composites as well. There are 3 areas that need to be addressed: replication with minimal stress so as to produce a high quality figure; attachment of support of the mirror segment so as to maintain the figure quality; and, thermal control requirements. Here we present a discussion of the requirements that lead us to select replication as the fabrication technology and the advantages of replication. We report on our first results of making a concave mirror and testing support methods of flats.