PSWG March 20081 Adaptive Optics Systems Engineering on GMT
Peter McGregor
Slide 2
PSWG March 20082 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
Slide 3
PSWG March 20083 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
Slide 4
PSWG March 20084 New ASM AO Paradigm Instrument AcqCam NGS WFS
LGS WFS Phasing Cam T-T-F WFS Truth WFS PWFS Active Opt. WFS
Slide 5
PSWG March 20085 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?
Slide 6
PSWG March 20086 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 200810 Full AO WFS System Phasing Camera NGS WFS LGS
WFS
Slide 11
PSWG March 200811 GLAO LGS WFS
Slide 12
PSWG March 200812 Complete Instr. Support Unit Phasing Camera
NGS WFS LGS WFS Calibration Unit 3.5 m
Slide 13
PSWG March 200813 Complete Instr. Support Unit
Slide 14
PSWG March 200814 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
Slide 15
PSWG March 200815 Full AO System + GMTIFS
Slide 16
PSWG March 200816 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
