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GMT Phasing

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

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GMT Phasing

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

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

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

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

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