Session 7 Special test Cryo-optical test of the PLANCK reflectors

2nd International Workshop onVerification and Testing of Space Systems

Session 7Special testSpecial test

Cryo-optical test of the PLANCK reflectors

Author(s): S. Roose, A. Cucchiaro(Centre Spatial de Liège)

Speaker: Stéphane Roose (e-mail :[email protected])

Torino 20/21/22 March 2006

Speaker: S. Roose (CSL) Torino 20/21/22 March 2006 2


Summary

• 1.Project Historical Background• 2.Overall Description• 3.Test results• 4.Lessons learned



1. Project Historical Background• PLANCK reflectors: 2 CFRP off -axis ellipsoids (Primary and secondary reflector)

• Measure relative SFE difference (293K and 50K) measurement method with a resolution of about 1 m (small deformations) on a SFE characterised by high SFE slopes at cryo-genic temperature (1 mrad) with INFRARED INTERFEROMETRY

WFE reconstruction simulation of the Primary reflector, through the CSL IR interferometer, based on expected deformation at 50 K,512 by 512 pixels detector



2.1. Overall Description: Secondary reflector (Single pass interferometer)

OM2

OM2C

F

Thermal shroud

Reflector support

Illumination optics

Interferometer cavity bench

Planck SR

Collecting optics

Optical bench

Vacuum flange with ZnSe windows



2.2. Overall Description: Primary reflector (Double pass interferometer)





3.1. Test results Secondary reflector QM: Full aperture test

Reflector not measurable in CRYO with this set-up: fringe density (slopes) too high! How Much?

Interferogram: 293 K Interferogram: 50 K WFE: 50 K



3.2. Test results: Secondary reflector QM and FM reduced field test

increased resolution derive new estimate for the slopes = 2 mrad

PLANCK SECONDARY MIRROR - FLIGHT MODEL - REDUCED PUPIL TEST - FM 1

name_ref "SRFM_1_1_293K_08DEC04_ZOOM1x_MOYENNE_REM9_corrige facteur 2.TXT"

name "SRFM_1_1_50K_17DEC04_ZOOM1x_MOYENNE_REM9_corrige facteur 2.TXT"

eti diff( ) 5.023 max diff( ) 15.01 min diff( ) 18.864 µm WFE

di 2 dj 1

1210 8 6 4 2 0 2 4 6 8 1012

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k

diff k colonnetab min tab( )

max tab( ) min tab( )255

0 50 100 150 200 250 300 350 400 4501210

864202468

1012

diff ligne k

k

ligne 210

colonne 245

WFE difference between 293 K -50 KSecondary reflector FM on central aperture



• Test results Secondary Reflector FM: New optical design

Increased slope collection: larger optics (4 inch diameter)Increased resolution: stitching to form composite image of the SFE

3.3. Test results Secondary reflector FM: New optical design



3.4. Test results: Secondary reflector FM Stitched aperture validation-compare interferometry with 3D data

PLANCK SECONDARY MIRROR - FLIGHT MODEL

ASED measurements projected through all optical system

eti R( ) 10.261 max R( ) 62.536 min R( ) 53.934 µm WFE

50 25 0 25 50700

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k

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Rk colonne Ik colonnefig tabR( )

0 50 100 150 200 250 300 350 400 450 500 550 600 650 70050

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Iligne k

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ligne 342

colonne 272

ZeR

10.6

0.072

0.049

0.097

0

0.895

0.424

0.02

0.413

1.263

PLANCK SECONDARY MIRROR - FLIGHT MODEL - test 2

name "SRFM_2_1_295K_26JUN05_3STIT.mca"

eti I( ) 10.788 max I( ) 82.439 min I( ) 47.24 µm WFE

50 25 0 25 50700

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ZeI

10.6

3.979

3.592

0.479

1.07

2.141

2.36

2.102

0.586

1.883



dj2 146

di2 411

dj1 429

di1 164

colonne 272

ligne 342

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µm WFEmin D( ) 59.909max D( ) 50.322eti D( ) 8.472

name_ref name


name_ref "SRFM_2_1_295K_26JUN05_3STIT.mca"

PLANCK SECONDARY MIRROR - FLIGHT MODEL - test 2 PLANCK SECONDARY MIRROR - FLIGHT MODEL - test 2 - data integrity at 50K

name_ref "SRFM_2_1_50K_30JUN05_1STIT.mca"


name_ref name

eti D( ) 0.17 max D( ) 2.972 min D( ) 3.108 waves WFE

2 1 0 1 2700

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Dk colonnefig D0( )

0 50 100 150 200 250 300 350 400 450 500 550 600 650 7002

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Dligne k

k

ligne 338

colonne 97

WFE difference between 293 K -50 KMeasurement repeatability RMS WFE

1.7 micron (SFE 0.9 micron)

3.5. Test results: Secondary reflector FM at 50 K



fig sphe( )

max sphe( ) 6.871

min sphe( ) 4.738

moy sphe( ) 0

et sphe( ) 0.477

Contribution of the spherical aluminium mirror RMS WFE = 0.5 μm

col 195column

lig 220line

limit 20limit for the plot =/- µm

stdev_diff 5.552standard deviation of DBL PATH WFE in µm

mi_diff 20.355minimum of DBL PATH WFE in µm

ma_diff 20.077maximum of DBL PATH WFE in µm

Tdi min diff( )max diff( ) min diff( )

255

20 10 0 10 20511

383.25

255.5

127.75

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k

diff k col

0 50 100 150 200 250 300 350 400 450 50020

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diff lig k

k

name_r "PRFM_1_1_298K_2MAY05_ZOOM2x_01"

name "PRFM_1_2_170K_8MAY05_ZOOM2x_pup1_OPD_1"

DIFFERENCE : NAME - NAME_R

PLANCK PRIMARY REFLECTOR FLIGHT MODEL PUPIL 1

Primary reflector Central aperture: WFE difference between 293 K - 170 K

3.8. Test results: Primary reflector FM



col 604column

lig 695line

limit 50limit for the plot =/- µm

stdev_diff 8.162standard deviation of DBL PATH WFE in µm

mi_diff 48.51minimum of DBL PATH WFE in µm

ma_diff 45.396maximum of DBL PATH WFE in µm

Tdi min diff( )max diff( ) min diff( )

255

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0 100 200 300 400 500 600 700 800 900 1000 1100 1200 130030

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difflig k

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name_r "Coma175\PRFM_1_1_298K_2MAY05_ZOOM2x_3STIT"

name "Coma175\PRFM_1_1_170K_11MAY05_ZOOM2x_1STIT"

DIFFERENCE : NAME - NAME_R

PLANCK PRIMARY REFLECTOR FLIGHT MODEL FULL PUPIL - STITCHING

Primary reflector Stitched full aperture:

170 K - 298 K

Reliable measurement down to 170 K (halve of the temperature excursion) Slopes ( estimated 2 mrad) are to high for the optics (based 1 mrad)



4. Lessons Learned

Are the Planck reflector tests a generic case for the future optical testing cases?

More and more for microwave to sub-mm reflectors: require testing!

-Slopes (non optical surfaces)-1-10 micron metrology resolution-high spatial sampling rate < 5 mm-non-contact measurement at very high (> 330 K) or very low T<90 K)

Commercial of the shelf measurement methods do not meet all requirements! (no market for it)

-3D machine (drawbacks: non vacuum, stable T, low sampling rate)-videogrammetry (drawbacks: sampling rate , intrusive targets)-infrared interferometry (drawbacks: no global shape, slopes)-holography (drawbacks: still under development)-lasertracker (drawbacks: non vacuum, contact)



Reflector development needs to consider testing problem very early in the project!

Why?

-thermal-elastic models do not tell the absolute truth: over-sizing the metrology tool might be necessary (increase test complexity). (PLANCK reflectors: wrong starting hypotheses in the assessment of commercial IR interferometry feasibility)

-allow to iterate with small scale test and metrology which addresses the hard-points. (PLANCK reflectors reduced field test)

-accept the non-universality of a method: divide and conquer, develop several simple test(PLANCK reflectors: SFE with interferometry (CSL) and global shape with videogrammetry (AAS-Cannes))

-early adaptation of method to the thermal vacuum test to allow technology developments. (Planck reflectors: Videogrammetry targets at low temperature (ESTEC), High resolution IR interferometer, Holography (CSL))

Documents

Session 7 Special test Cryo-optical test of the PLANCK reflectors