Fundamental AO Design Issues for TMT

1
Fundamental AO Design Issues for TMT

• Pacing the design and development effort
• Scientific utility, cost, technical risk
• Mix of facility and dedicated AO systems
• Wavefront correction
• Wavefront sensing
• Laser guide star (LGS) generation and projection
• Large-stroke, high-order wavefront correction
• Large stroke, high order deformable mirrors (DMs)
• Woofer-tweeter DM configurations
• Piezostack, MEMs, and/or an adaptive secondary
• Defeating LGS elongation
• Maximizing sky coverage

2
First Light (2014) AO Architecture
LGSFacility
(Active)Secondary
Narrow-FieldIR AO System
Narrow-FieldNear IR Instruments
3
Comprehensive AO Architecture
LGSFacility
Wide-Field Near IR Imager
Secondary
Multi-Conj.AO System
Narrow-FieldNear IR Instruments
Multi-ObjectAO System
Multi-ObjectSpectrograph
Mid InfraredAO System
Mid IR Instrument(s)
Extreme AO System
Planet FormationImager/Spectrometer
4
Baseline AO Component Summary
NGS AO
LGS AO
5
Narrow Field IR AO System (NFIRAOS) Specifications
6
NFIRAOS Strawman Design Concept
z
LGSWFS
NGSWFS
Dichroic beamsplitter
Fieldderotation
Narrow fieldIR instrument(s)
High-orderDM
Fieldstopmirror
Low-order,large-strokeDM (if needed)
Science NGS LGS
Telescopefocalplane
Off-axis parabolarelay
7
Notional MCAO First Light Error Budget
8
Remaining AO Modes and their Issues

• MOAO (IRMOS)
• Near IR tip/tilt sensing and MEMS
• Open loop wavefront sensing and DM control
• ExAO (PFI)
• Near IR wavefront sensing?
• Coronography and calibration for speckle
  suppression
• MIRAO (MIRES)
• Cool or cryogenic DM?
• Near IR NGS, LGS, or multiple LGS AO?
• GLAO (WFOS?)
• Number and type of guidestars performance vs.
  FOV
• Upgrade paths
• Large stroke correction using an adaptive
  secondary, or woofer deformable mirrors in each
  AO system?
• Deformable mirror and laser technologies for
  NFIRAOS/MCAO with 120 nm RMS WFE