PSWG March Adaptive Optics Systems Engineering on GMT Peter McGregor

PSWG March Top-Level Questions:  Will GMT queue schedule instruments? What instrument configuration time is acceptable?  Will GMT have general-purpose ports? What field of view?  Will the upper IP support non-AO instruments? What field of view? What acquisition/calibration support?  Will M1/M2 be phased “intrinsically”? If extrinsic, what FoV/magnitude star is required?  What are the advantages of using an ASM?  What is optimal AO instrument performance?  How can maximum AO sky coverage be achieved? What TTWFS patrol field?  Yes 5 min  Yes 5 arcmin  Yes 5 arcmin Full  Yes ?  TBD TBD

PSWG March Proposed Solution:  5 arcmin folded Gregorian focus on upper IP +/- 75 arcsec AO engineering field +/- 30 arcsec AO science field  Integrated acquisition and calibration facilities  Multiple (4-6) non-AO & AO instrument ports  Rapid reconfiguration between instruments  Maximum cryogenic AO system and instruments  Maximum AO tip-tilt WFS patrol field  Minimum interference in science path

PSWG March New ASM AO Paradigm Instrument AcqCam NGS WFS LGS WFS Phasing Cam T-T-F WFS Truth WFS PWFS Active Opt. WFS

PSWG March Outstanding Issues:  Does M1 phasing require a 10 arcmin patrol field? Does this invalidate the concept? Or does it demand an intrinsic telescope solution?  How should field/pupil rotation be compensated? Large diameter ferro-fluidic hermetic seals? Implications for servicability?  How to calibrate LGS AO system with ASM?  Are non-common path phase errors acceptable?  Where to locate the IR instrument cold stop?  Should GMACS/NIRMOS have exclusive access? Do they restrict on AO designs?

PSWG March Non-AO Support Requirements  Multiple (6?) instrument ports 5 arcmin diameter FOV  2 Peripheral Wave Front Sensors Maintain independent tip-tilt-focus of 7 M1 segments Active optics monitoring Instrument rotator monitoring  Acquisition camera  Instrument (& WFS) calibration unit

PSWG March Wave Front Sensor Drum

PSWG March Acquisition Camera

PSWG March AO WFS Requirements  > 3 NGS tip-tilt/focus near-infrared WFS (> 60” rad.)  6 LGS high-order WFS (35” radius)  1 high-order optical NGS WFS (on-axis)  1 high-order optical(?) truth WFS  M1 segment phasing WFS

PSWG March Full AO WFS System Phasing Camera NGS WFS LGS WFS

PSWG March GLAO LGS WFS

PSWG March Complete Instr. Support Unit Phasing Camera NGS WFS LGS WFS Calibration Unit 3.5 m

PSWG March Complete Instr. Support Unit

PSWG March At Second Focus…  Tip-tilt-focus wave front sensors for LTAO  Truth wave front sensor Minimize non-common path errors  Science instrument…  All with field derotation

PSWG March Full AO System + GMTIFS

PSWG March Summary  Demonstrated a feasible implementation of AO at the f/8 Gregorian focus  Optics are large and complex  Consequences of moving to an f/16 feed should be considered  More work is required to: Improve optical performance Develop concepts for science instruments (GMTIFS, MOAO, MCAO) Include WFSs at second focus Address field derotation on a stationary Instrument Platform Consider 10 arcmin(?) diameter phasing camera patrol field