Transcript LGSs at the 4.2m William Herschel Telescope

CANARY
Laser Guide Star
Multi-Object Adaptive Optics (LGS MOAO)
E-ELT PATHFINDER
Richard Myers
ON-SKY
DEMONSTRATOR
FOR EAGLE
Durham University
Royal Astronomical Society
1
Overview


CANARY Collaboration
LGS MOAO







Falcon: 8m MOAO (study)
EAGLE: 42m MOAO
General
EAGLE
Technical challenges
Principles of CANARY demonstrator


Why “CANARY”?
Rayleigh LGS
Role of WHT
Demonstration stages and timescales
CANARY: MOAO demo on
4.2m WHT on La Palma,
Canary Islands
Risk mitigation
Current status

Funding status
9 May 2008
RAS
2
CANARY Consortium
Observatoire de Paris LESIA Durham University
ONERA
Isaac Newton Group
UK Astronomy Technology Laboratoire d’Astrophysique
Centre
de Marseille
Fanny Chemla, Eric Gendron, Zoltàn Hubert, Aglaé Kellerer, Michel Marteaud,
Gérard Rousset, Fabrice Vidal, Ali Basden, Sofia Dimoudi, Nigel Dipper, Colin Dunlop,
Deli Geng, Andres Gueselaga, Dani Guzman, Mark Harrison, Tim Morris, Richard Myers,
James Osborn, Chris Saunter, Gordon Talbot, Laura Young, Eddy Younger,
Don Carlos Abrahams, René Rutten, Thierry Fusco, David Henry, Andy Longmore,
Brice Leroux
Overlaps with EAGLE AO design team and SESAME team
9 May 2008
RAS
3
Laser Guide Star
Multi-Object
Adaptive Optics
(LGS MOAO)
LGS MOAO Schematic
[Courtesy ESO]
9 May 2008
RAS
4
EAGLE MOAO requirements
and baseline implementation






NIR Multi-Integral Field Unit (IFU) for 42m E-ELT
Wide IFU patrol field ≥ 5 arcmin with ≥ 20 such IFUs
≥ 30% energy in 0.075 arcsec spatial element in H-band
Multiple LGS (≥ 6), multiple NGS (≥ 3)
Closed loop control of M4 telescope adaptive mirror
Open loop control of high order (≥ 100x100 actuator)
Deformable Mirror (DM) in each IFU channel
9 May 2008
RAS
5
Technical challenge and proposed
mitigation

Open loop control of high
order DMs


calibration
Staged On-sky Demonstration
of SINGLE channel:
CANARY: 2010-2012
ELT LGS



Laboratory Demonstration:
SESAME: working now
Spot elongation
High accuracy wide field
tomography
Goals:
* demonstrate MOAO in
EAGLE configuration,
* verify design models,
* develop techniques,
e.g., calibration, RTC
Real-time control (RTC)


Algorithms
Scale of implementation
9 May 2008
RAS
6
LGS Wavefront Sensor (WFS)
Spot Elongation
due to sodium layer depth
(central LGS)
Cone
Effect
LGS
turbulence
WORSE for ELTs
9 May 2008
WORSE for ELTs
RAS
7
CANARY LGS MOAO demo method
Key technology: RAYLEIGH LGS (RLGS)
(e.g., SOR, WHT, MMT, SOAR, LBT LGS study)

These use pulsed lasers with temporal WFS range gating

to select LGS height and extension (range gate depth)
The Rayleigh LGS Altitude and extension are programmable
 They can emulate the spot elongation & cone-effect
geometry of a SODIUM LGS on a MUCH LARGER
telescope


SO:
85 km sodium LGS → 8.5km Rayleigh LGS
 10km sodium layer → 1km range gate depth
 42m E-ELT → 4.2m WHT


In principle: can emulate sodium density evolution too
9 May 2008
RAS
8

BUT:

However…
This scaling is not perfect
Atmosphere and wavelength are not scaled
 There will be additional uncorrected turbulence in demo
compared to ELT
 Need to reduce LGS separation to emulate ELT metapupil overlap at a given altitude


SO NEED:
Concurrent Natural Guide Star (NGS) tomography
 Record corrected wavefront (truth sensor) as well as
the near-IR image (Point Spread Function)


9 May 2008
To check that current MOAO correction is as predicted
for current atmosphere
RAS
9
William Herschel Telescope


4.2m Alt-Az, La Palma
Operational Rayleigh LGS: GLAS
Grond-laag Laser Adaptieve optiek Systeem
(Ground-layer Laser AO System)


18 W 515nm
Launch System


Safety Infrastructure



No fly zone
Launch permission
Traffic Control


35cm telescope above M2
MK clone
MASS/DIMM 20m from WHT

9 May 2008
SCIDAR 340m from WHT
RAS
10
GLAS WHT LGS Facility
ING - Astron - Durham
NAOMI AO System:
UKATC-Durham-ING
INGRiD imager: ING
OASIS IFU: Lyon
Variation of closed-loop (●) and open-loop (○) Gaussian fit
FWHM versus angular distance from centre of field for a 20s
J-band image. Turbulence profile approx 50% at ground, 15%
at 4km, and 35% at 16km. LGS altitude of 15km.
9 May 2008
RAS
11
GLAS Software Description
9 May 2008
RAS
12
WHT Nasmyth
(GHRIL)



Large, undedicated
Nasmyth enclosure for
guest instruments
2.5 × 1.34 m opt bench
Services
9 May 2008
RAS
13
GHRIL
NASMYTH
9 May 2008
RAS
14
CANARY Demo Stages

Phase A 2010



Phase B 2011



3 × Natural Guide Stars (in 3’ field) open loop control of low
order (8 × 8 actuator) Deformable Mirror (DM)
Natural Guide Star Truth Wavefront Sensor, Near-IR imager
Add 4 × LGS open loop control of low order DM
Concurrent NGS tomography maintained
Phase C 2012



Closed loop LGS/NGS control of low-order DM
Open loop control of high-order DM (up to 32 × 32
actuator)
Full-up EAGLE demo
9 May 2008
RAS
15
Phase A : NGS MOAO

Components:




Low-order 8x8 DM
3 x EMCCD open-loop NGS WFSs
Open-loop optimised Fast Steering Mirror (SPHERE design)
Diagnostic Systems:



1 x EMCCD closed-loop NGS WFS (Truth Sensor)
High speed DM figure sensor
NIR Imaging camera (loan courtesy ESO)
Phase A: NGS MOAO
WHT
Nasmyth
9 May 2008
Science
Verification
GHRIL
Derotator
NGS
Pickoffs
Calibration
Unit
3 x NGS
WFS
NGS
FSM
Low-order
DM
Truth
Sensor
Figure
Sensor
RAS
16
Phase B: Low-order LGS MOAO
GLAS
BLT
WHT
Nasmyth
Diffractive
Optic
GHRIL
Derotator
Calibration
Unit
LGS
Rotator
GLAS
Laser
LGS
Dichroic
NGS
Pickoffs
NGS
FSM
LGS
Pickoffs
3 x NGS
WFS
Low-order
DM
LGS
FSM
Science
Verification
4 x LGS
WFS

Figure
Sensor
Truth
Sensor
Phase B: Low-order LGS MOAO
New modules include:


9 May 2008
Electronically shuttered LGS WFS CCD (Lincoln Lab)
Modified GLAS launch, LGS dichroic and relay system
RAS
17
Phase C: High-order LGS MOAO
GLAS
BLT
WHT
Nasmyth
Diffractive
Optic
GHRIL
Derotator
LGS
Rotator
NGS
FSM
Figure
Sensor
GLAS
Laser
Low-order
DM
Calibration
Unit
Phase C: High-order woofer-tweeter
LGS MOAO (woofer closed loop)
LGS
Dichroic
NGS
Pickoffs
LGS
Pickoffs
3 x NGS
WFS
LGS
FSM
MEMS
DM
Science
Verification
Truth
Sensor
4 x LGS
WFS

Closest resemblance to proposed EAGLE MOAO implementation




Closed-loop low-order DM conjugated to ground layer
Open-loop MEMS DM
SPARTA (ESO VLT) type accelerated Real-Time Computer
NOTE: LOW-ORDER LTAO CAPABILITY
9 May 2008
RAS
18
Key
Components

NGS WFS


LGS WFS


Adonis (ESO 3.6m)
High order DM


Phase A NGS Design: Paris LESIA
Surface Sensing
SPHERE Design
Low order DM


Lincoln Lab
Gated CCDs
Fast Steering Mirror


E2V EMCCDs
(asterisms with
4 NGS
in 3’ needed)
BMM 32 × 32 MEMS – just delivered
Real-time Computer

PC-based with Evolution to
ESO SPARTA system
9 May 2008
RAS
19
“De-Risking”

Figure Sensor (DMC)



RTC



High-speed LUPA 300
CMOS detector
+ FPGA (IAC collab)
Proof of concept trial
currently being integrated
in Durham
First version based on working PC-based system
Contract with ONERA/Shaktiware
On-site component tests October 2008



LGS asterism test: Diffractive Optical Element (Herriot-Watt)
Gated CCD test on-sky
Test Figure Sensor in WHT environment
9 May 2008
RAS
20
Phase A Space Envelope
At WHT Nasmyth
Current Status

NGS main path optomechanical concept complete



LGS pickoff and relay optical
design complete
2 simulations running



Alignment/calibration
procedures
using YAO run by A. Kellerer
Using Durham AO simulation
platform (DASP) by A. Basden
Phase B Optics
Next:

Comparative simulation using
EAGLE design codes


Design Reviews June 2008


ONERA/Durham
Phase A PDR, B/C CoDR
RTC first contract June 2008
9 May 2008
RAS
21
PHASE B
9 May 2008
RAS
22
Phase C
9 May 2008
RAS
23
9 May 2008
RAS
24
9 May 2008
RAS
25
Funding Status




UK (STFC)
France (various)
EU FP7 Preparatory
Fund
EU OPTICON JRA-1 – applied




Funded, enough for first two phases
ESO-led
Includes additional WHT nights
Further STFC support for final phase - applied
Further French funding proposals - to be made
9 May 2008
RAS
26