1. GMT Phasing GLAO – not needed LTAO – Phase stabilization done at ~1kHz with edge sensing at M1 and M2 – Phase reference set at ~.01Hz using off-axis star by measuring stabilized fringes from sub-aperture – Atmospheric phase errors are ignored with some loss of Strehl because not enough photons available to measure NGS – phase can be measured from guide star (pyramid sensor?)

2. 2 Phasing across gap for off-axis star 315 270 225 180 135 90 45 0

3. MEMS mirror array Cryostat window/field stop Lenslet array Dichroic Electron multiplication CCD Cryostat window Visible channel field lens Relay lens or pupil viewer lens IR channel field lens Filter IR relay lens IR Detector 300mm Andor camera window

5. Telescope focus or pinhole. Warm relay Removable Phase adjuster Turbulence phase screen (lab tests) MEMS tip-tilt mirror array Offner relay Visible tip-tilt camera Cryostat IR Fringe Detector

7. Springs Offner Mirror Upper cylinder Prisms Annular plate Lower cylinder MEMS board