e-elt programme pre-focal wave front correction and field stabilization for the e-elt l. jochum, n....
TRANSCRIPT
E-ELT Programme
Pre-focal wave front correction and field stabilization for the E-ELT
L. Jochum, N. Hubin, E. Vernet, P.-Y. Madec, M. Dimmler, M. Mueller, B.Sedghi
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 2
Outline
E-ELT optics layout
E-ELT AO components
Main axes control
Field Stabilization Unit
Adaptive Unit
Conclusions
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 3
E-ELT Optics Layout
Surface shape Diameter (mm) Distance (mm)
M1 Concave ellipse 42000 36500
M2 Convex hyperbola 5691 36500
M3 Concave sphere 4032 13645
M4 flat 2636 x 2587 10000
M5 flat 2978 x 2388 34563.72
5 mirror adaptive telescope
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 4
Disturbers Atmospheric turbulence Windload Gravity and thermal effects
Task for E-ELT pre-focal AO real time wave front correction for the
E-ELT focal plane, reaching diffractionlimit of the telescope in the NIR
Correction devices Telescope main axes control Field stabilization mirror Adaptive mirror Wave front sensing systems
NGS, LGS, laser sources, beam transport and launch, WFS, RTC
E-ELT AO components
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 5
Main axes control
Residual of main axes control input disturbance for image stabilization
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 6
M5 – Field Stabilization Unit
Task: Tip tilt correction forimage stabilization
Components: Mirror Field stabilization system Mounting structure Control system Auxiliary Equipment
Incoming disturbance: 1” rms residual tip tilt Dominated by wind shaking
10-2
10-1
100
101
102
10-12
10-10
10-8
10-6
10-4
10-2
100
102
Frequency [Hz]
PS
D [a
rcse
c2/H
z]
wind shakingatmosphere
Conservative assumptions:•10m/s wind speed @ 10 m•No dome•30% safety margin
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 7
M5 correction
Required output Residual on sky tip-tilt:
< 0.07” rms (goal 0.06”) over the entire frequency range
< 0.004” rms for [9Hz to ] all peaks < 2σ
Conditions:
WFS sampling: 100Hz
RON no noise
WFS delay 10 ms
RTC delay 1 ms
Phase margin >45 deg
Modulus margin >0.6
Communication with RTC[25 - 1200]Hz
Remaining wave front correction adaptive mirror with positioning system
E-ELT control simulation:main axes + M5
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 8
M4 – Adaptive Unit
Components:Adaptive mirror, Positioning system,Mounting structure, Control system, Auxiliary Equipment
Tasks: correction of……small amplitude residual tip-tilt…high order wavefront (real-time)
Atmosphere wind shake low spatial frequency telescope errors
…large amplitude low frequency tip-tilt…lateral pupil position
Telescope gravity Thermal load adapter tracking wobble & run-out errors
Nasmyth foci selection
Adaptive mirror
Positioning system (4 DoF)
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 9
M4 positioning system requirementsPupil Lateral correction
Range (mm) ± 20 mm
Min Continuous speed (mm/s) speed ≥ 1 mm/s
Absolute accuracy (µm) ≤ 100 µm
Resolution (µm) ≤ 50 µm
Bandwidth (Hz) > 1 Hz
Mechanical tilt correction
Range (") ± 120 (±14" on sky)
Speed ("/s) 10 (1.2"/s on sky)
Absolute accuracy (") 0.5 (0.06" on-sky)
Resolution (") 0.25 (0.03" on-sky)
Cross coupling
Between Tip & tilt (mech ") 0.25
Between lateral & tilt (mech ") over full range
0.25
Between lateral & tilt (mech ") during any time period of 0.2 s
0.025
Between tilt & lateral (µm) < 50
Between two lateral (µm) < 50
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 10
Adaptive mirror main requirements
Fitting error: 145 nm rms (goal 110)
Temporal error: 60 nm rms (goal 43)
Tip-tilt after M4: 1.3 mas @ 1 kHz WFS sampling
Total stroke defined for worst seeing conditions (2.5arcsec seeing, 100 m outer scale)
Optical quality, mass, power consumption, dynamic behavior, passive stability (lookup tables), environment, ….
High reliability (key element for E ELT)
under median seeing conditions
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 11
Required tip-tilt correction after M4
Incomming disturbance:0.119” residual on sky rmsafter telescope & M5 correction
Wavefront sensor sampling
frequency (Hz)
Loop delay
ms
Res. on-sky tip-tilt errors (mas rms)
100 11 9
290 4.5 3.5
700 2.4 1.6
1000 2 1.3
1200 1.8 1.3
Conservative assumptions:10m/s wind speed @ 10 mExponential wind profileNo dome30% safety margin in original data
E-ELT control simulation:main axes + M5 + M4
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 12
3 step disturbance correction
Telescope main axes control
M5
M4
1.3 mas residual rms error compatible with diffraction limit in NIR
Remaining tip tilt < 1” rms
Low frequency, high stroke
High frequency, low stroke
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 13
Conclusions
E-ELT will be an adaptive telescope, NIR diffraction limited In-built Field stabilization mirror In-built adaptive mirror
Demanding requirements pushing state of the art technology
Feasibility studies, conceptual and preliminary design, breadboarding and prototyping of critical components carried out by industry under ESO contracts
16h00 Armando Riccardi, 16h40 : Daniele Gallieni E-ELT M4AU development at Microgate
16h20 Bruno Crépy, 17h20 Jean-Christophe Sinquin E-ELT M4AU development at CILAS
17h40 Javier Barriga E-ELT M5FU development at NTE
E-ELT Programme
L. Jochum @ AO4ELT – June 2009 Slide 14
c'est tout