More information: http://www.ctio.noao.edu/~atokovin/soar/

• Do we need AO?
• What can and can not be done with AO?
• System concept and performance
• Preliminary plan

The case for high angular resolution is evident! See images with 0.3" and 0.7" resolution.

• Rival 8 m telescopes in background-limited sensitivity
• Best ground-based sensitivity in crowded fields

• Optical: UNIQUE capability, 0.03" resolution
• IR: lose to Gemini 2 times in resolution, 4 times in sensitivity, 16 times in exposure time to reach given S/N.

Source: Gemini RPT-AO-G0094

Improve wave-front coherence at r₀ scale .

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Idea 1: Low-order compensation = incoherent combination of 1 m sub-apertures. Example: CFHT+PUEO. Gain in FWHM: ~2 times. Small FOV.

Idea 2: Compensate only low layers. Gain in FWHM: ~2 times. Large FOV.

• Several NGSs and tomography (but: not enough photons)
• Rayleigh LGS: good, insensitive to high layers!

PSFs under good seeing at 0.67 micron:

Full line: uncompensated (leftmost) and with tip-tilt.

Dashed line: AO+LGS at 10 km.

Improve wave-front coherence across full aperture.

• Need NGS -> small sky coverage (but: LMC, Galactic plane!)
• Small compensated FOV

PSFs under good seeing at 0.67 micron with 12^m NGS. The leftmost PSF is for uncompensated image under same conditions.

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Limiting magnitude?

Strehl ratio on-axis and at 4" off-axis versus NGS R-magnitude. Good seeing, 0.67 micron.

PUEO: 1-m sub-apertures -> 15^m

SOAR: 0.5-m sub-apertures -> 13^m?

• Compensation changes the PSF structure: becomes more peaked
• Maximum gain in Strehl and FWHM
• Lower gain in encircled energy and detectivity

Good match between seeing-improved resolution in the visible and seeing limit in the IR.

• Small (~1 m size) AO module on the optical ISB
• DM: OKO Tech, 35 mm beam diameter, 70-120 actuators
• WFS: Shack-Hartmann, curvature or pyramid (TBD)
• LGS: Rayleigh, solid-state UV laser, 10-20 km altitude
• TTS: three sensors, to be used with LGS
• Three scientific instruments, switchable
  • Imager: 2K CCD, red-optimized, pixels 100 and 15 mas
  • IFU spectrometer: 2 plate scales
  • Third instrument: TBD, reserved for future

• 2001: Simulations, WFS concept definition
• 2002: Closed-loop laboratory simulator AND conceptual design.

  Decision to build the AO system.

• 2003: Final design, fabrication
• 2004: Integration, testing, commissioning (NGS mode)
• 2005: LGS upgrade

RESOURCES:

2002 - NOAO internal (design study)

2003-2005: NOAO+SOAR? $500K?

Summary: We want to design a USEFUL system which combines unique high-resolution capability in the optical with seeing improvement mode. It must be cheap!