PALM-3000

High-order Wavefront Sensor Update

Christoph Baranec

Team Meeting #9

10/22/2008

PALM-3000HOWFS Overview

Since last team meeting #7…

• Analysis of crosstalk due to diffraction estimated to have non-zero, yet small impact.

• Optical design finalized.• Summer SURF student (M. Feldman) tested the

CCD50 and initial optical alignment.• Procurement status.• Beginning to assemble final sensor assembly.

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PALM-3000Optical Design

3http://www.astro.caltech.edu/~baranec/publications/SPIE_7015-206.pdf

PALM-3000Flexibility in Optical Design

• Final collimating mirror to be defined.– Focal length will be determined by AO system optical relay F/#

(as built).– Selection of spherical vs. parabolic surface to be determined by

ellipticity needed in final system lenslet to DM geometry. TBD.• A spherical surface will introduce > 1% ellipticity. This also requires

a cylindrical lens for static astigmatism correction on the detector. These elements are economical and fast to fabricate.

• A parabolic surface can project a circular pupil. This will incur a greater cost and delivery time.

• Determined that a sub-set of the HOWFS lenslets (ie. 56x56 vs. 64x64, 28x28 vs. 32x32, etc.) can be used if determined to be necessary by the relay-HODM-LODM design.

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PALM-3000Summer Detector Characterization

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CCD50 and integrating sphere with computer controlled LED source

Summer student, M. Feldman

•Setup CCD50 in basement of Robinson.•Able to control camera via Scimeasure software.•Testing of gains, dark current and read noise. (Some difficulties controlling camera due to inexperience.)•Initial results are ‘similar’ to published values from Scimeasure and E2V.•Final SURF report due end of next week. Example gain calculation

PALM-3000Summer Optical Setup

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PALM-3000CCD50 images (Summer ‘08)

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CCD50 image of the 32 x 32 lenslet array configuration.(unfortunate colormap…)

PALM-3000Lab Equipment

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Fully stocked lab to support HOWFS integration. All located in Robinson

basement lab.

PALM-3000Procurement

• All stock optics in hand, including alignment tools.

• All non-lenslet array optical mounts in hand.• Lenslet arrays delivered. We have 10 of each of

the 64x, 32x and 16x arrays, 5 each of the 8x arrays. (If anybody needs an extra one…)

• Motion control (lenslet array exchange and alignment, relay focus) is in hand.

• Collimating optics TBD.• Lenslet array mount needs to be fabricated.• Unclear about reuse of ‘current’ spatial filter.

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PALM-3000Optical Components

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PALM-3000Motion Control

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PALM-3000What’s next…?

• Integration of the HOWFS in a final version– Fabrication and alignment of lenslet array exchanger.– Assembly of alignment jig.– Assembly of all current parts.– Maybe even initial baffling

• Further characterization of CCD50 (at some point…)

• Please see the e-Drawing of the HOWFS

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