OPTICON AOJRA1 M1 Meeting

1
VLT ADAPTIVE SECONDARY DESIGN STUDY(straw-man
design phase)
A. Riccardi(INAF-Osservatorio di Arcetri)
2
OUTLINE

• Arcetri and MMT/LBT adaptive secondary units
• Planned activity, tasks and deliverables where
  we are now
• VLT DMS dimensioning for straw-man design
• VLT shell figuring specifications

3
TECHNICAL CONTEXT

• system specs definition/review design
  overview(P30-P36-MMT336-P45-LBT672)
• optical calib. testing of protos and final
  units manufactured by MGADS(P30-P36-P45-LBT672)
• control law design and system optimization (with
  DIA MG)(P30-P36-MMT336-P45-LBT672)
• engineering (Lab) SW(P30-P36-MMT336-P45-LBT672)
• AdSec Supervisor SW (Telescope
  release)(P45-LBT672)

MicrogateADS produced/are producing all
theprotos and telescope units (MirrorLab for
optics)
4
VLT DM2 DESIGN PLAN
TIME TASK To 3M Phase 1 I/Fs analysis
and straw-man design 4M ? 8M Phase 2
Deformable mirror surface quality and
dynamical performance validation 9M ?
13M Phase 3 Conceptual design and analysis 14M
? 21M Phase 4 Preliminary design 22M ? 30M
Phase 5 Final design
Tomid June 2004
5
VLT DMS DESIGN PLAN - Phase 1
Phase 1 VLT I/Fs analysis and Adaptive
Secondary straw-man design DURATION 3
MONTHS START June 2004 TASKS Specs
review system parametric analysis
- system dimensioning
- allowed figuring
error Support to Microgate-ADS OUTPUT
system dimensioning tool (Excel
file, straw-man dimensioning)
spec on figuring error document
(straw-man analysis) RESOURCES 0.3 FTE
Done
Done
Done
Done
Ready
Almost ready
6
VLT DMS DESIGN PLAN NEXT PHASE
Phase 2 Deformable mirror surface quality
and dynamical performance validation DUR
ATION 5 MONTHS START T05mo TASKS P45
prototype dynamical tests with new digital
electronics Optical measurements for magnet
gluing tests Support to Microgate-ADS OUTPUT
Test Reports (as input to ESO/Microgate for
Consolidated Design) RESOURCES 0.8 FTE
7
INAF contribution to straw-man design

• Scaling laws and simplified dimensioning
  formulas for straw-man design first-order
  computation of system parameters (fine tuning
  needs FEA provided during phase 3 conceptual
  design and analysis).

Input parameters
Output parameters
The excel file is a deliverablethat is provided
to all JRA1 partners
8
Model for the straw-man dimensioning analysis

• Infinite plate of constant thickness
• edge effect neglected
• finite RoC effect neglected
• Regular square grid of actuators
• ring pattern -gt square pattern with average same
  density
• Localized position-velocity control loop Force
  Feed-forward

Shell thickness t, Actuator pitch L
Force for turb. correction Ft t3/L2
Actuator efficiency e L3/2
Dissipated Power in the coil P (F/e)2 t6/L7
Requested electronic/natural damping D BW M
BW L2
Trade-off between shell thickness, actuator
pitch and power dissipation
9
Analysis results
Nact1170 (96mmltdlt1120mm), pitch28.9mm (21cm on
M1)
10
Analysis of allowed figuring error of thin shell

• Actuators can compensate for shell figuring
  error
• Limitations
• no correction for scales d lt 2 L ? HF figuring
  error (HFE)
• force limitation correcting scales d gt 2 L
• correcting scales d gt 2 L some extra-error
  (harmonics) is introducedat scale d lt 2 L ?
  print-though error (PTE)

How to specify those limitations?
Shell figuring do not have to limit the
performancesof perfect AO with serendipity
seeing (0.2arcsec?)
11
Figuring spec concept
L actuator pitch
wf PSD
r0best best seeing (0.2 arcsec)
Spatialfrequencyk
12
Figuring spec concept
13
OBTAINING FIGURING SPEC CONCEPT
14
FIGURE ERROR SPECTRAL DENSITY
r050cm_at_500nm seeing0.20 asec t2.0mm force rms
0.16 N force peak0.6 N t1.8mm force rms0.11
N force peak0.4N (spec 0.1 N!!!)
15
SHELL FIGURING SPECIFICATION
red line new envelopto give fmax0.1N