Widening the Scope of Adaptive Optics

Matthew Britton

The Seeing Limit

Atmospheric Turbulence

Wavefront phase

Seeing limited image

Diffraction limited image

Long Exposure PSFs

Diffraction limit

Seeing limit

Seeing limit (x40)

Angular Resolution

~ D0

Point source Sensitivity

~ D2

Angular Resolution

~ D

Point source Sensitivity

~ D4

Palomar Seeing on Aug 20, 2005

Turbulence Profiles

Seeing Limited PSFs

Adaptive Optics

Adaptive Optics

NGC 7469 (CFHT)Neptune (Keck)

NGC 3603(VLT)

Anisoplanatism

Modeling the PSF

OTFoa = OTFgs * ATF

An Experiment at Palomar

Observations of a 21” Binary

Guide Star

Companion

OTFgs * ATF = OTFoa

Turbulence theory

Cn2 profile measurements

Observed and Predicted PSFs

Strehl Ratios vs. Time

Predicted vs. Measured Strehls

Fitting the Observation

I(r) = OTFgs(r) + d * OTFoa(r) * exp{i r}

d = differential photometry = differential astrometry

Differential Photometry

2.12 m .7903 +/- .0004

1.65 m .8316 +/- .0007

Relative Intensity

Differential Astrometry

2.12 m 21.3322 +/- .0006 282.3923 +/- .0011

1.65 m 21.3306 +/-.0012 282.3932 +/- .0023

Observations of a Quadruple

Modelling the Observation

LGS Adaptive Optics

Laser Tilt Indeterminacy

Pilkington 1987 (Nature)

Adaptive Optics with Lasers

LGS PSFs on a 10 m Aperture

Keck LGS observationOf M5

(Courtesy of the CfAO Treasury Survey)

Advanced Wide Field Adaptive Optics

A Preliminary Comment

Field dependence of the AO system performance is a function of:

• Aperture diameter• Observing wavelength• Guide star configuration• How the adaptive mirrors are deployed• Zenith angle• Turbulence conditions (-> time)

Single Laser AO (SLGLAO)

Poor to moderate performance over a modest field

FOV = 70” (D / 30 m)(90 km / h)

Ground Layer AO (GLAO)

Poor performance

Field uniformity

Tomography

Laser Tomography AO (LTAO)

Good performance on axis

Multiconjugate AO (MCAO)

Good performance over 30” field

Multiobject AO (MOAO)

Intermediate performance over 5’ field

Conclusions

There are a number of ways to provide wide field AO compensation.

• Postprocessing using turbulence profiles• XXAO

At least one of them is likely to work for your observations…