Torino 18/19 March 2003 1

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Session 6Special TestSpecial Test

Design of the cryo-optical test of the PLANCK reflectors(S. Roose (CSL), A. Cucchiaro (CSL), & D. de Chambure (ESTEC))

Speaker:S. Roose(Centre Spatial de Liège)

Torino 18/19 March 2003 2

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Introduction: the test objectives

•PLANCK reflectors: 2 CFRP off -axis ellipsoids to be tested separately (SR: 1050 mm x 1100 mm) (PR:1550 mm x 1890 mm)

•measure the surface figure error (SFE) difference between 293K and 40K•measure the focus displacement between 293K and 40K

Speaker: S.Roose

Torino 18/19 March 2003 3

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Surface figure error measurement: the challenges

•relative SFE measurement method with a resolution of about 1 m (small deformations) on a SFE characterised by high SFE slopes (1 mrad)

•relative focus displacement measurement with 20 m accuracy (PR inter-focal distance: 21 m)

Speaker:S. Roose

Torino 18/19 March 2003 4

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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...the challenges (cont’d)•proposed method wavefront measurement method in stigmatic configuration (single pass for SR, double pass for PR)

Speaker:S. Roose

Laser

Reflector

Thermal shroudLens

Lens

To measurement device

Thermal shroud

Primary reflector

Convex spherical mirror

Lens

Torino 18/19 March 2003 5

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Infrared interferometry

•SFE is hidden in the wave-front measured by the interferometer•operational wavelength:10.6 m •WFE resolution < 1 m •high wave-front sampling rate (detector resolution): 320 x 240•increased resolution possible with sub-aperture stitching •wave-front slope limitation: l wavelength per 4 pixels•slope limitation translated at reflector level (SFE slopes): 0.1 mrad (PR), 0.2 mrad (SR).•in principle incompatible with predicted slopes, but...

Speaker:S. Roose

Torino 18/19 March 2003 6

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Infrared interferometry (cont.d)•simulation of interferogram recording and processing

Speaker:S. Roose

•secondary reflector at 40 K (worst case)•use of a standard interferometer with sub-aperture stitching

Torino 18/19 March 2003 7

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Infrared interferometry (cont.d)

Speaker:S. Roose

•primary reflector at 40 K (worst case)•need of high resolution interferometer (800 by 800 pixels)•IR interferometer (1200 by 1200 pixels) under development

Torino 18/19 March 2003 8

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Hartmann test (back-up solution)

•wave-front slope measurement method•dynamic range scalable (at the price of sampling rate)

•centroid precision 0.1 pixel•dynamic range of 10 pixel•campling rate: 20•incompatible with specs.

Speaker:S. Roose

d

c

Wavefront

Pinhole Array

Detector-array

pixel pixel

subaperturesN

N

2

Torino 18/19 March 2003 9

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Hartmann test (cont’d)

Speaker:S. Roose

SR-SFE reconstructedwith 64 by 64 samples

PR-SFE reconstructedwith 100 by 100 samples

•commercial instrument not available•new concept: high sampling rate with dynamic Hartmann test

Torino 18/19 March 2003 10

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Secondary reflector test configuration

Speaker:S. Roose

OM2

OM2C

F

Thermal shroud

Reflector support

Illumination optics

Interferometer cavity bench

Planck SR

Collecting optics

Optical bench

Vacuum flange with ZnSe windows

Torino 18/19 March 2003 11

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Secondary reflector test configuration (cont’d) •interferometer camera and laser outside vacuum chamber•interferometric cavity on 5 DOF outside thermal shrouds•illumination optics mounted on 3 DOF outside thermal shrouds•metrology for focus search:1) LVDT to measure PR I/F wrt CSL I/F (<10 m)2) T° regulation of optical bench and supports (<0.2 K)(<5 m)3) stigmatic image (minimize WFE):(<2 m)

Speaker:S. Roose

Torino 18/19 March 2003 12

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Primary reflector test configuration

Speaker:S. Roose

Planck PRVacuum flange withZnSe optical windows

Interferometric cavity bench

Thermal shroud

Convex spherical mirror

Torino 18/19 March 2003 13

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Primary reflector test configuration (cont’d) •interferometer camera and laser outside vacuum chamber•interferometric cavity on 5 DOF outside thermal shrouds•convex spherical mirror (Diameter 1500 mm): inside shrouds mounted 3 DOF•metrology for focus search:1) LVDTs to measure PR I/F wrt CSL I/F (<10 m)2) T° regulation of optical bench and supports (<0.2 K)(<5 m)3) stigmatic image (minimize WFE):(<2 m) 4) in situ radius measurement of contraction of spherical mirror: (<0.1 ppm) ) or (<3 m)

Speaker:S. Roose

Torino 18/19 March 2003 14

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Reflector cool-down

Speaker:S. Roose

Secondary reflector cool down

0

40

80

120

160

200

240

280

320

0 20 40 60 80 100

Time (h)

Tem

pera

ture

(K

)

Secondary reflector

Primary reflector cool down

0

40

80

120

160

200

240

280

320

0 20 40 60 80 100

Time (h)

Tem

pera

ture

(K

)

Convex spherical mirror

Primary reflector

•Radiative cooling•Thermal control of conductive I/F (0 Watt)

•Permanent losses via optical apertures

Torino 18/19 March 2003 15

1st International Workshop onTest Philosophies, Standards, Methods and Quality for Space Systems

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Conclusions

•SR test foreseen in FOCAL 3 facility, July 2003•PR test foreseen in upgraded FOCAL X facility, december 2003

•Challenges:•Manufacturing of convex spherical mirror•Manufacturing of high resolution IR interferometer

Speaker:S. Roose