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,

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

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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