palm-3000 status of the palm-3000 high-order adaptive optics system a.h. bouchez, r.g. dekany, j.r....
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PALM-3000
Status of the PALM-3000 high-order adaptive optics system
A.H. Bouchez, R.G. Dekany, J.R. Angione, C. Baranec, K. Bui,R.S. Burruss, J.R. Crepp, E.E. Croner, J.L. Cromer, S.R. Guiwits,
D.D.S. Hale, J.R. Henning, D. Palmer, J.E. Roberts,M. Troy, T.N. Truong, J. Zolkower
SPIE Optics and Photonics, San Diego
8/3/2009
PALM-3000Talk Outline
• Science Case– Performance predictions– Project 1640 coronagraphic IFS
• Subsystems– Optical Relay Design– Deformable Mirror Testing– High Order Wavefront Sensor Assembly– Wavefront Processor Computer Design
• Future plans
PALM-3000The PALM-3000 upgrade
The Palomar AO system• 241 actuators, 16x16 sampling, 2 kHz max
frame rate• Typical perf.: 190 nm RMS WFE• Instruments:
– PHARO nIR imager & spectrometer– Project 1640 nIR coronagraphic IFS– SWIFT visible IFS– Visitor instruments
The PALM-3000 upgrade• 3388 active actuator deformable mirror• Wavefront sensor with up to 63x63 pupil sampling• Wavefront reconstructor computer to run at up to 2 kHz• Expected performance:
– 90 nm RMS WFE in median conditions (r0=9.2 cm)– 79 nm RMS WFE in 75th percentile conditions (r0=11.0 cm)
Palomar AO & SWIFT installed on the 5.1m Hale telescope
PALM-3000
4
Science Drivers
• Galactic– Hot, young exo-Jupiter studies– Faint debris disks– Mass/luminosity of pre-main sequence binariesRequire high contrast in the near-infrared
• Solar system– Io surface geology– Multiplicity of TNOs and asteroids– Surface minerology
of large asteroidsRequire high Strehl in the visible
PALM-3000 will deliver >50% Strehl in V band!
2.5”
Brown et al., ApJ 639, 2006
Oppenheimer et al., AJ 679, 2008
Marois et al., Science 322, 2008
PALM-3000
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The Project 1640 Instrument
• PI: Ben Oppenheimer, American Museum of Natural History
• Apodized Lyot coronagraph with a low-resolution (/=30) J-H band integral field spectrograph back-end.
• Post-coronagraphic calibration wavefront sensor being developed by JPL.
• Expected flux ratio reached at 1.0” radius from bright stars (3 in 1 hr):– PALMAO 8 x 10-4
– P3K 5 x 10-6
– P3K + JPL Cal 2 x 10-7
Raw spectra of a broadband calibration source Project 1640 in the lab at AMNH
PALM-3000Project 1640 early results
Recently discovered companion, contrast ~10-3 (Oppenheimer et al, in prep.)
PALM-3000Optical Relay
• Reuses existing bench, off-axis parabolas, steering mirrors, tip/tilt mirror, science dichroics, DM (DM241). Retain current science focus position
• New HOWFS, high-order DM (DM3388), Acquisition Camera and Stimulus
• Passes 120” Ø field
• DM3388 located at pupil, 10.5° AOI
• DM241 located at +742 m conjugate, 16.0 ° AOI
• Requires 4 fold mirrors (meets 50% transmission requirement, incl. telescope)
• Acquisition camera rides on HOWFS focus stage
DM3388
DM241
OAP1TTM
FM3
FM4
FM1
FM2
OAP2
SSM1
SSM2
HOWFS & ACam
ScienceInstrument
Volume
PALM-3000Optical Relay Performance
Corner of PHARO (20”, 20”)
Corner of P1640 (2”, 2”)
M1 aberration (2 µm P-V astigmatism) 14 mas 1.4 mas
Atmosphere (median conditions, 2) 21 mas 2.1 mas
TT anisoplanatism 20 mas 2 mas
Optical Performance
• On-axis aberrations corrected by DMs (astigmatism from dichroic, alignment errors)
• Field aberrations 30” off axis are ~32 nm RMS
• Woofer DM at non-pupil conjugate leads to focal plane distortion, on same scale as tip/tilt anisoplanatism
Mechanical Tolerances• <5 mas image drift over 300s in
the focal plane
Image shift induced by applying corrections for these errors at +742 m conjugate
J band spot diagrams at science focus, using DMs to correct on-axis aberrations
• <5% misregistration of finest subaperture in 300s in pupil plane
• Requires both careful mechanical design and active, open-loop compensation
PALM-3000High-Order Deformable Mirror
• Xinetics photonics module PMN• World’s highest actuator count
deformable mirror– 66 x 66 = 4356 actuators on 1.8
mm pitch
– We control 3388 on 112 mm
• Manufacturing completed in June 2009– 1.8 µm stroke measured
– Restricted to 1.4 µm by HV supplies
– 9% stroke uniformity
• Currently undergoing final acceptance testing
66x66 actuator mirror before face sheet bonding
PALM-3000Deformable Mirror Testing
• All actuators are functional• Influence functions are ~1 actuator spacing FWHM• Unpowered surface figure 150 nm RMS, significantly
worse than expected but meets science requirements
Zygo map of mirror surface, with ~100 nm surface actuation.
PALM-3000DM Electronics and Cabling
Implementation issues• Driver electronics dissipate ~4 kW; must be mounted on telescope due to cable volume• Cables require redesign to meet observatory operational requirements
PALM-3000High Order Wavefront Sensor
• Shack-Hartmann design with selectable 8, 16, 32 or 63 samples across the pupil
• CCD50 detector (128x128 pixels) in SciMeasure Lil’ Joe camera
• Uses a tilted spherical collimator and cylindrical lens to match mircrolenses to DM3388 actuators at 10.5º AOI
See Baranec, Proc. SPIE 7015, 2008.
PALM-3000HOWFS microlens arrays
• Images of the microlens arrays in the assembled HOWFS arrays taken with a CMOS alignment camera.
PALM-3000HOWFS alignment
• Spot patterns recorded with the CCD50 camera
• Preliminary alignment:
Pupil sampling
RMS s lope (pixe ls)
RMS wavefront (nm; Zern ike 1-20)
63 0.038 102 32 0.066 166 16 0.150 143 8 0.175 150
PALM-3000HOWFS Subaperture Alignment
63 63 32 32 16 16 8 8
• In the 63x63 subaperture mode, the pupil will be shifted with respect to the detector to preserve Fried geometry. In the other modes, we will use use modal control.
PALM-3000Wavefront Processor Computer
• Perform full matrix multiplication reconstruction!• Parallelize, and use off-the-shelf Graphics Processor
Units for computation• House GPUs in a remote cluster of low-cost desktop
PCs (in observatory computer room)
Implementation• VMM calculations performed on 16 Nvidia GPUs in 8
PCs– Advantages: Low cost, simple software implementation,
rapid upgrade cycle• PC 0 provides the interface, scheduling, and control of
the cluster• PC 9 is dedicated to telemetry recording (1 Tb RAID,
Berkeley DB)• Communication provided by a Quadrics switch (latency
measured to be 19 µs)• All running Real-Time Linux• Publish/subscribe environment
Strategy• Despite reconstruction problem being 250 times larger than for present-day systems…
8192 slopes x 3631 actuators, vs. 512 slopes x 243 actuators
PALM-3000Servo Control Architecture
Flexible control system
Modes:
1. Control DM3388 & TTM, offload to DM241
2. Split modes btw. DM3388 & DM241, offload to TTM
3. Fixed DM241 (good seeing only)
4. Calibration WFS input to centroid offsets & DM3388 positions
PALM-3000Future Plans
PALM-3000 Testbed• Demonstrate performance of all new components before taking
Palomar AO system offline– Includes all PALM-3000 components except DM241, final optics (eg. off-axis parabolas, stimulus), and steering mirror mounts
– Low-cost monochromatic source and refractive optics
• Beginning integration of testbed in August 2009• Goal is to demonstrate closed-loop operation at 2 kHz by February
2010
Future Milestones• Project 1640 Cal WFS integrated with Palomar AO Dec. 2009• PALM-3000 pre-ship review planned for June 2010• First light in February 2011