Progress Toward the 6.5-m MMT Infrared Adaptive Optics System

In late 1996, the existing six mirrors of the Multiple Mirror Telescope (MMT) will be replaced by a single 6.5-m mirror, which is now being polished at the Steward Observatory Mirror Lab. Earlier work [1, 2] has shown that an adaptive optics system using a single sodium laser projected co-axially with the telescope can provide imaging at the diffraction limit in the H and K photometric bands over most of the sky. In the design of the system for the 6.5-m, we will project a 4-W beam from a continuous-wave dye laser from a refractive launch telescope [3] located behind the secondary mirror. Returning light will be corrected for the effects of atmospheric turbulence at the secondary mirror, which will be a 2-mm thick continuous facesheet whose shape can be modified at 1 kHz update rate by 300 voice-coil actuators. The major components of the system are shown in the schematic of Figure 1.