The construction of extremely large telescope is only possible with a segmented primary mirror. The phasing of the
primary mirror due to its size and its number of segments is a main concern at the European Southern Observatory. The
European Southern Observatory has developed a test bench called Active Phasing Experiment to study new phasing
technology and new telescope control system. The key subsystem of this experiment is a scaled down Active Segmented
Mirror (ASM) composed of sixty-one hexagonal segments of seventeen millimeters side to side. Each hexagonal mirror
can all be controlled in piston, tip and tilt. The integration of this jewel piece of opto-mechanic started after the
successful results obtained with the manufacturing of a prototype composed of only seven modules.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.