the vis instrument for euclid · 2011-09-30 · euclid consortium euclid consortium meeting bologna...

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Euclid Consortium Meeting Bologna 7-8/9/11

The VIS instrumentfor Euclid

Mark Cropper UCL-MSSL, UK

Richard Cole UCL-MSSL, UK

Ady James UCL-MSSL, UK

Jerome Martignac CEA, F

Stephane Paltani U of Geneva, CH

Anna Di Giorgio IFSI, Rome, I

Jean-Jacques Fourmond, F

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VIS Management Diagram

Mark Cropper

VIS Instrument Lead

Richard Cole

VIS Project Manager

Phil Guttridge

VIS Electronics

Engineer

Dave Walton

VIS Detector Scientist

ECB and

Euclid Consortium Lead

Y Mellier

Ady James

VIS System Engineer

Martin Kemp

VIS Mechanical

Engineer

ROE Design Team

J-J Fourmond

CU Manager

IAS

S Paltani

UoG

Alan Spencer

Product Assurance

J-L Augueres

FPA Manager

CEA

A Di Giorgio

CDPU Manager

IFSI

ESA

VIS Simulation Team Instrument

Scientist

ESA

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• Large area focal plane of CCDs

– 6x6 array e2v CCD273 – customised for Euclid

– Tight psf – CCD contribution to FWHM in range 0.073‟‟-0.094‟‟ (radiation damage an issue)

• 2 band survey

– 2 CCDs operating in narrow band

• Low temperature operation

– Very stable thermal environment, ±0.3K over 3740s

• Low noise CCD readout

– 4.5electrons noise

– Slow readout possible - 70kHz

• Shutter to prevent light falling on CCDs in readout

– Not frame transfer CCDs (area impact)

– Mechanical

• Calibration function

– Flat field calibration lamp

– Note: no „calibration shutter‟ – starlight on CCDs during flat field calibration

Key VIS functional requirements

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Product Tree

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Electrical Architecture

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Focal Plane Array (FPA)

VI-FPA Detector Plane

Mass (kg) 11.1

Power (W) 1.7 + 3.6

I/F Temp. (K) 148 ± 2

VI-FPA Electronics Housing

Mass (kg) 42.0

Power (W) 111.8

I/F Temp. (K) 235 ± 5

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Read-out Shutter Unit (RSU)

VI-RSU

Mass (kg) 8.3

Power (W) 1 (max), 0.03 (av)

I/F Temp. (K) 150K

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VI-CU

Mass (kg) 0.8

Power (W) 0.7 (max)2e-3 (av)

I/F Temp. (K) 150K

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Command and Data Processing Unit (CDPU)

VI-CDPU

Mass (kg) 13.7

Power (W) 53.8

I/F Temp. (K) 288 ± 35

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Power Management and Control Unit (PMCU)

VI-PMCU

Mass (kg) 10.5

Power (W) 28

I/F Temp. (K) 288 ± 35

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• Simple operations

• Science Modes

– Table below

• Other modes

– Standby

– Engineering

– Survival

– Safe

VIS Operational Modes

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Shutter Cal Unit N_exp Exp_duration

Normal Observation Sequence opens off 4 540

Linearity Sequence opens off 4 10,50,150,540

Flat Field Sequence opens on 3 10

Dark Sequence closed off 1 540

Bias Sequence closed off 1 1

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• VIS Requirements

– Definition of final requirements

– Flow down to lower levels

• Contamination

• Light tightness (stray light)

• Shutter

– Simplify redundancy concept

• FPA

– FPA mechanical concept – SiC to Aluminium interface

• CDPU

– Data compression ratio

• Programme duration

– IPRR panel: underestimated by 6m

• CCD

– Lower noise/lower speed – OK

– Radiation shielding/margin to be improved

VIS issues after IPRR

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Weak Lensing Performance

Mark Cropper, Jerome Amiaux, Henk Hoekstra, Tom Kitching, Richard Massey, Lance Miller, Sandrine

Pires, Jason Rhodes

and many others in the WL Working Group and elsewhere

The presented document is Proprietary information of the Euclid Consortium. This document shall be used and disclosed by the receiving Party and its related entities (e.g.

contractors and subcontractors) only for the purposes of fulfilling the receiving Party's responsibilities under the Euclid Project and that identified and marked technical data

shall not be disclosed or retransferred to any other entity without prior written permission of the document preparer.

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Weak Lensing Requirements

Level 1

Level 2

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• True two-point correlation function affected by additive bias s2

sys and multiplicative bias M

• more simply:

… with simple values calculated for ai and mi

Weak Lensing Requirements (ctd)

PSF sizes and ellipticities

errors in PSF sizes and ellipticities (knowledge) universe

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Top level requirements

MRD PERD DPR

(+ MOCD etc. see Jerome’s talk)

• Analyses indicate that in order for systematic bias effects to be lower than the random errors from the survey size/galaxy number additive bias s2

sys<107; multiplicative bias M<2x10–3

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PSF knowledge

• Main contributions:

PCA CTI effects

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Simulations: instrument

optics

pointing

detector pixel

detector radiation damage

CCD

mosaics

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Data Processing: CTI algorithm

• Bristow & Alexov (2003) algorithm further developed for HST

data processing by Massey, Rhodes et al.

• “Read” image through CTI model (eg CDM03) in combinations and make linear combinations

• Rapid convergence achieved in practice

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CTI correction: residual ellipticity

• The residual ellipticity in faint galaxies furthest from the readout node, after correction during image postprocessing shows requirement met for ~4.5 e– RMS readout noise for perfect model

• Model parameters can be adjusted to null out residual CTI effects on detector coordinates model imperfections can be reduced sufficiently

Massey, Rhodes et al

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PCA: principles

• Decompose PSFs into a basis set using Principal Components Analysis

• Use model data to establish PSF basis set

• Fit real star to get component coefficients

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PSF knowledge: modelling approach

• Stars on each dither frame allow the PSF to be monitored as a function of position and exposure sequence

• Create a 3-D model of the PSF as a function of space and instrument state

• Decompose into PCA components

• Check if PSF can be reconstructed to within the requirements

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Number of PCA components

• Number of PCA components is limited to <20 for

– spatial components

– temporal components

– both

– multi-wavelength components

for the model PSFs

• effectively ~1800 stars per exposure available to characterise the PSF in a cube of images

sufficient information to characterise PSF in principle

spatial temporal both multiwavelength

2020 20 20

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PCA Knowledge: requirements met

• Detailed modelling using shows that requirements are met using PCA modelling, with

– model PSFs as priors,– high fidelity simulated data (noise, pixellisation…) – real distribution of star brightnesses

for monochromatic data

(see Lance Miller‟s talk for update)

Size residualsEllipticity residuals

requirement

requirement

field

of

vie

w

field

of

vie

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Summary

• For Weak Lensing/VIS a coherent structure has been set in place which translates cosmic parameters to requirements on the instrument

• Given sufficient sensitivity and survey size, shear measurements depend primarily on the PSF knowledge with main contributors

– CTI effects modelling/correction

– the system PSF modelling

• An end-end chain of simulations has been developed which creates high fidelity data from VIS

• A comprehensive analysis has been made of

– the information content of the PSF and the ability to model it

– the ability to deal with the CCD CTI effects

• Detailed knowledge of the important issues has been achieved

• These comprehensive analyses indicate that all driving requirements are met

the vis instrument for euclid · 2011-09-30 · euclid consortium euclid consortium meeting bologna...

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