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

Session 7 Special test Cryo-optical test of the PLANCK reflectors Author(s): S. Roose, A. Cucchiaro (Centre Spatial de Liège) Speaker: Stéphane Roose (e-mail :sroose@ulg.ac.be). Torino 20/21/22 March 2006. 1.Project Historical Background 2.Overall Description 3.Test results

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

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  1. Session 7 Special test Cryo-optical test of the PLANCK reflectors Author(s): S. Roose, A. Cucchiaro (Centre Spatial de Liège) Speaker:Stéphane Roose (e-mail :sroose@ulg.ac.be) Torino 20/21/22 March 2006

  2. 1.Project Historical Background 2.Overall Description 3.Test results 4.Lessons learned Summary Torino 20/21/22 March 2006

  3. 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 Torino 20/21/22 March 2006

  4. 2.1. Overall Description: Secondary reflector (Single pass interferometer) Torino 20/21/22 March 2006

  5. 2.2. Overall Description: Primary reflector (Double pass interferometer) Torino 20/21/22 March 2006

  6. Torino 20/21/22 March 2006

  7. 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? WFE: 50 K Interferogram: 293 K Interferogram: 50 K Torino 20/21/22 March 2006

  8. 3.2. Test results: Secondary reflector QM and FM reduced field test increased resolution derive new estimate for the slopes = 2 mrad WFE difference between 293 K -50 K Secondary reflector FM on central aperture Torino 20/21/22 March 2006

  9. 3.3. Test results Secondary reflector FM: New optical design • 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 Torino 20/21/22 March 2006

  10. 3.4. Test results: Secondary reflector FM Stitched aperture validation-compare interferometry with 3D data Torino 20/21/22 March 2006

  11. 3.5. Test results: Secondary reflector FM at 50 K Measurement repeatability RMS WFE 1.7 micron (SFE 0.9 micron) WFE difference between 293 K -50 K Torino 20/21/22 March 2006

  12. 3.8. Test results: Primary reflector FM Contribution of the spherical aluminium mirror RMS WFE = 0.5 μm Primary reflector Central aperture: WFE difference between 293 K - 170 K Torino 20/21/22 March 2006

  13. 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) Torino 20/21/22 March 2006

  14. 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) Torino 20/21/22 March 2006

  15. 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)) Torino 20/21/22 March 2006

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