MCAOMCAO

A Pot Pourri: AO vs HST, the A Pot Pourri: AO vs HST, the Gemini MCAO and AO for ELTsGemini MCAO and AO for ELTs

Francois Rigaut, GeminiGSMT SWG, IfA, 12/04/2002

December 4,2002 GSMT SWG 2

UH-88”, Courtesy W.Brandner, 0.65” seeing

Filters:

•H•K’ •CO•CO cont.

4’

IRS7 SgrA*

>10 stars per arcsec2 at K~18

Bow shock

Very high extinction clouds

40”

5”

>220 stars in 5”x5”

IRS8 (bow shock)

December 4,2002 GSMT SWG 3

• Arches Cluster 2.2 micron image. Young Star cluster in Galactic center region (10 Million years old)– Up-left: HST/NICMOS– Up-right: Gemini/Hokupa’a– Lower-right: Gemini/seeing 0.5”

December 4,2002 GSMT SWG 4

• Gemini goes ~ 5-10x deeper• Angular Resolution :

– HST = 0.19”– Gemini = 0.13”

Luminosity Function

December 4,2002 GSMT SWG 5

HST/NICMOS

Gemini/Hokupa’a

December 4,2002 GSMT SWG 6

December 4,2002 GSMT SWG 8

December 4,2002 GSMT SWG 9

This figure shows a ten minute exposure of GG tau using this

technique compared to the HST/NICMOS image from Silber et al. (2000). The

Hokupa'a image comfirms the suspected gap in the disk that fell in the diffraction spikes of

HST/NICMOS as well as revealing new structure in the

disk.

GuyoGuyonn

December 4,2002 GSMT SWG 10

MPE Group: GC resultsMPE Group: GC results

QuickTime™ and a YUV420 codec decompressor are needed to see this picture.

December 4,2002 GSMT SWG 11

NAOS resultsNAOS results

December 4,2002 GSMT SWG 12

Classical AO

MCAO

No AO

165’’

MCAO Performance SummaryMCAO Performance SummaryEarly NGS results, MK ProfileEarly NGS results, MK Profile

2 DMs / 5 NGS

320 stars / K band / 0.7’’ seeing

1 DM / 1 NGS

Stars magnified for clarity

December 4,2002 GSMT SWG 13

Effectiveness of MCAOEffectiveness of MCAO

Numerical simulations:• 5 Natural guide stars• 5 Wavefront sensors• 2 mirrors• 8 turbulence layers• MK turbulence profile• Field of view ~ 1.2’ • H band

QuickTime™ and a YUV420 codec decompressor are needed to see this picture.QuickTime™ and a YUV420 codec decompressor are needed to see this picture.QuickTime™ and a YUV420 codec decompressor are needed to see this picture.

December 4,2002 GSMT SWG 14

PSF CharacteristicsPSF Characteristics

• H Band• [16,17,8] actuators• Median seeing, CP• 200 PDE/sub/ms for

H.Order WFS• Least square

MCAO

AO

Distance off-axis [“]

Stre

hl r

atio

FW

HM

[ar

csec

]

Distance off-axis [“]

50%

Enc

.En.

[“]

0.1”

Slit

Cou

plin

g

Distance off-axis [“]

Distance off-axis [“]

0.7 mag

IFU: > 1 mag

3x

10x

Most of area is here !

December 4,2002 GSMT SWG 15

The Gemini MCAO in brief...The Gemini MCAO in brief...

• Baseline system (17,19,12) actuators across beams, 3DMs, 5 WFS+LGS (125 PDE/subaperture/frame ~ 10W)

• Field average Strehl under median seeing conditions at zenith (no NGS noise)Band AO-only SS Overall SS * FWHM Limiting mag†

J 41% 20% 0.032’’ 26.3 H 60% 40% 0.042’’ 25.0 K’ 75% 60% 0.057’’ 24.9*includes mostly low order aberrations from telescope and

instrument, and AO calibration errors. † 5 sigma in 1 hour, extrapolated from the Hokupa’a results

• H band Sky Coverage : 15% (b=90o), 70% (b=30o)

December 4,2002 GSMT SWG 16

MCAO, CAO, HST & NGST MCAO, CAO, HST & NGST SensitivitiesSensitivities

Limiting magnitudes, 5, 3600sec, aperture = 2x2pixelsMedian seeing No AO MCAO HST NGST

R~5 [magnitude (nJy)] m 23.2 (370) 24.9 (76) 23.7 (230)23.2 (370) 24.9 (76) 23.7 (230)28.0 (4.4)28.0 (4.4) m 24.8 (190) 26.3 (50) 26.0 (66)24.8 (190) 26.3 (50) 26.0 (66)28.6 (6.0)28.6 (6.0)

R~10000 [magnitude (Jy)] m 20.4 (4.8)20.4 (4.8) 20.3 (4.8) 17.2 (92) 20.3 (4.8) 17.2 (92)

20.1 (6.1)20.1 (6.1) m 21.3 (4.7)21.3 (4.7) 20.5 (9.7) 17.9 20.5 (9.7) 17.9 (107)(107) 20.5 (9.7)20.5 (9.7)

slit width (at K) 0.4” 0.066” 0.22” 0.066”

Chun et al:• confirmed spectroscopy 1 < < 2.5 m will be detector limited Nearly half (11/25) of the DRM’s can be started and explored by Gemini The MCAO Science Case workshop

December 4,2002 GSMT SWG 17

Various AO modes and first order Various AO modes and first order performanceperformance

December 4,2002 GSMT SWG 18

Relative Gain of groundbased 20m and 50m telescopes compared to NGST

Gro

un

db

ased

ad

van

tag

eN

GS

T a

dva

nta

ge

1 101E-3

0.01

0.1

1

10

1001 10

1E-3

0.01

0.1

1

10

100

50m R=10,000

20m R=10,000

Wavelength (m)

1 101E-3

0.01

0.1

1

10

1001 10

1E-3

0.01

0.1

1

10

100

50M R=5

20m R=5

S/N

Ga

in

Wavelength (m)

ImagingImaging Velocities ~30km/sVelocities ~30km/s

December 4,2002 GSMT SWG 19

ELT-AO Fundamental ELT-AO Fundamental ChallengesChallenges

Sky Coverage (independent of D)S.C. 0.1% (V), 2% (K), 20% (L-M)

Solutions: Laser Guide Stars Multiple faint Natural GSs

LGS Cone effect: S exp[- (D/d0)5/3] Scone(1 m) = 0.5 (8-m), < 0.01 (50-m)

Solution: Multiple beacons

90 k

m

Path diff. and “Missing” Data

Open-loop measurements of off-axis LGS(large dynamic range, sensitivity loss)Solution: Multi-Conjugate AO

December 4,2002 GSMT SWG 20

Scaling and Orders of Scaling and Orders of magnitudemagnitudeversus D FoV 1 2 3

#DM - -1.2 3 6 6#act/DM D2 -2.4 (1+a)2 3000 30000 125000 #WFS/GS - - (1+b)2 5 6 6#pix/s/WFS D2 -3.6 - 5.106 5.107 2.108

Computing Pow. D4 -6 (1+c)2 100GF 30PF 800PFLaser power* -/D/D2 -3.6 - 50W 80W 160W

1: D=30 m, S~30% @ =1 m, FoV= 1’2: D=50 m, S~30% @ =0.5 m, FoV= 2’3: D=100 m, S~30% @ =0.5 m, FoV= 2’

>>> Fundamental limits: #DM (, ), #GS > #DM <<<

Fov = 2’, ~ 6 DM / FoV = 4’, 15 DMs ! (at ~ 1 micron)* no smart tricks

December 4,2002 GSMT SWG 21

Sample Numerical ResultsSample Numerical Results(CP Turbulence, 3 DM’s)(CP Turbulence, 3 DM’s)

December 4,2002 GSMT SWG 22

CriticalCritical Technology to develop Technology to develop

• Deformable Mirrors :– Deformable secondaries (butable)– Dense / Compact DMs (d=1mm? 8’ waffers / 5mm

Xinetics)

• High speed CCD arrays for WFS• Fast computers/Alternative control schemes

– “segmented pupil”– Layer oriented WFSs

• Lasers (short pulses)

Cost: $50 to $100M. To be started ASAP. AO defines the ELT’s critical path !