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This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Freeform optics design and manufacturingMicrocarb
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Roland GEYL VP Business DevelopmentSafran Reosc
Journées freeform – Marseille – 12-13 Oct2017
Journées FreeformMarseille – Oct 2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
1.8-m GSD from 600 km orbit20x20x25 cm 3 payload volume
Freeform is a reality
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ELT M1 segments mass-productionwith freeform technology
MERLIN : Receiver fast & large M1
MicroCarb instrument On Myriades platform
High instrument compactnessthanks to
freeform optics technology
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Benefits of using freeform optics
The MicroCarb mission
Optics concept
Airbus-Reosc concurrent engineering
Preparing for manufacturing
Conclusion
Outline
3Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran4
Benefits of freeform
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Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Introduction of freeformFirst smart, then aggressive
BenefitsIncreased performance at DM1-M2 = 1300 mm
Reduction of DM1-M2 becomes possible
Gain in volume, mass & inertia !
Nota : also gain in distortion
Pleiades telescope freeform versionFrom smart to agressive freeforms
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DM1-M2 = 1300 mmVolume = 1.5 m3
DM1-M2 = 525 mmVolume = 0,9 m3
d = 800 mmVolume = 1,1 m3
Study case : Pleiades’ Korsch type TMA Aperture - F/# 650 mm - F/20Linear FoV 1.6° (Y) / 0.1° offset (X)Dist M1-M2 DM1-M2 = 1300 mm WFE (worst) 0,0083 λ = λ /120 RMSVolume ≈1.5 m3
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Recently UoR’s scientists published on the subjectImaging spectrometer are inherently non-symmetric due to the dispersive element that seperate the wavelengthsFrreform may therefore benefit
Case of an F/3.8 Offner-Chrisp concept
Freeforms also benefits to spectrographs1: Increasing performances
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Light; Science & Applications (2017à 6, Freeform spectrometer enabling increased compactness_J. Rolland_K. Thompson
Offner-Chrisp spectrometer
All-spherical All-aspheres With tilts & decenters All-biconic aspheres Freeforms
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Freeforms also benefit to spectrographs2: Enabling more compact configurations
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Light; Science & Applications (2017à 6, Freeform spectrometer enabling increased compactness_J. Rolland_K. Thompson
Nominal size / All-spherical More compact / All-spherical More compact / All Freeforms
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran8
MicroCarb
The CO2 cartographer
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Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Program decided in dec 2015 (COP 21)Jan 2016 Phase B fundedMar 2017 Decision of phase C-D fundingApr 2017 Partnership France-UKMay 2017 Kickoff Phase C-D-E Budget 75 M€Launch scheduled for 2020 (orbit 650 km)Lifetime 5 years
Mission Mapping sources and sinks of CO2, the most important greenhouse gas, on a global scale.First European program on the subject.Follows GOSAT (JP) & OCO-2 (US) High accuracy ≈ 1 ppmBias < 0,1 ppmBasic Pixel 4,5 x 9 km² Revisit 1 week
MicroCarb
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Measurement of absorbed & reflected solar flux in severalhighly resolved Vis & NIR spectral bands Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Installed on a Myriade platformMicrosat platform developed by CnesClasse 100 - 150 kg Modular & low cost access to space
Microcarb : compact but high performance
Thanks to its low global cost, MicroCarb aims to be precursor of a microsat constellation for accurate and continuous car bon monitoring.
MicroCarb : At the peak and cost-effective
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Used for PICARD, SSOT, SPIRALE, …
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
CNES selected Airbus for the development of the passive spectrometer instrument
The MicroCarb instrument
11Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Microcarb : An innovative instrument concept
12Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Microcarb : Optical principe
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Three Mirror Anastigmat
Three Mirror Anastigmat
Journées freeform – Marseille – 12-13 Oct2017
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Spectral characteristics
Safran REOSC / Confidential / Date / 14
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Optical configuration (1)
15Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Optical configuration (2)
16Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran17
Joint design work withAirbus
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Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Airbus Instrument optical designMecano-thermal architecture Spec evolution during Phase B Final decision
Work share
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Safran ReoscOptical manufacturingOptical metrologyRisk assessment & mitigationCommitment on specifications
Agreement to be found on Mirror type of definition (Zernike vs Polynomials) Feasability vs asphere departureCommitment on the WFE spec (15 nm RMS WFE)Commitment on scheduleEdge effects and edge margin needed
=> Compactness
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Option 1 : Classical referentialParent conic axis of first mirrorTilts & decenters of next mirrorsAsph + freeform terms
Optical elements referential
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Z
Y
Option 2 : Local referential on each mirrorIncidence vs « main chief ray » of each mirrorRadius at center of usefull areaFreeform terms
Building the reference system for an easier optimizati on
Other options also possibleAll give same results
=> Option 2 selected because it is more simple
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Zernike polynomialsPreferred by Safran Reosc
Zernike vs Polynomials
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Taylor expansion polynomialsInitially preferred by Airbus
���, �� � ���,�
And many others, …Chebychev, Legendre, NURBS, …
Reosc’s polishing & testing NC chainis based on Zernike.
Similar performance obtained in all cases=> Zernike representation selected
Forbes polynomials
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Three successive TMA 1. Relay the JWST image 2. Collimator3. Camera
Average characteristicsDimension 10x10 to 30x30 cmAsphere sag 10 to 400 µm Substrate RB SiC+ CVD SiC polishing layer WFE quality < 130 nm RMS for all trainEdge margin ≈ 1 mm
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COL & CAM needtight packaging for
volume & perf.
Aspheric departure : NIRSpec heritage
CAM mirrors Integrated CAM TMA Integrated COL TMAJournées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
Various designs submitted by Airbus during Phase B Mirror size in the range of 100x100 mm onlySome cases highly aspheric :
� Aspheric departure up to 1,5 mm� Slopes up to 30 mrd� Zernike up to Z36
Only M3-Tel is similar to NIRSpec
All others mirrors are significantly more aspheric� Asph departure = 450, 600, 1300 µm PTV
Polishing requirements : 15 nm RMS WFE
Discussion and exchanges
Agreement on most reasonnable values
Aspheric departure
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EUV ellipsoid mirrorSize 230x155 mmMargin 18 mmAsph 2.8 mm PTVSlope 70 mrad PTV WFE 25 nm RMS
Journées freeform – Marseille – 12-13 Oct2017
Wrt best sphere wrt best cylinder
Ex: M2 Spectro TMSClear aperture 100 x 75 mmAsph wrt best sphere 590 µmAsph wrt best cylinder 320 µm
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
1 mm margin only achieved on NIRSpec but : More tooling, work and schedule involvedRisks on polishing layer (CVD or R-SiC)
Airbus edge margin wish : < 5 mm
Safran Reosc initial wish : > 15 mm
Final edge value agreed : 12 mm for freeforms
(less for plano and spherical)
Edge margin
23Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran24
PREPARATION FOR MANUFACTURING
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Journées freeform – Marseille – 12-13 Oct2017
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CVD SiCMERSEN-Boostec has a 1.3-m CVD furnaceOperation remains long and risky
Schedule Risks� Preparation before CVD Deposition process� CVD deposition & inspections Chips along edges� Profile restoration after CVD Passing through the CVD during polishing� 10X more difficult polishing than glass
CVD SiC or R-SiC ?
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Safran Reosc R-SiC: Faster – Safer - LargerFast polishing like glass - Low roughness – Low BRDFEasy removal & redeposition in case of passing trhoughSelf funded intense R&T since several years� Demonstrator piece made for ADS (SPOT-6 mirror)
ESA Qualification on C-SiC and RB-SiCCapability up to 1600 mm in our large coaterLarge size demonstration under OTOS – TANGO program
Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
In the past years, focus was given on large optics. ELT M1 segments & large space optics
But small size freeform optics demand is growingNew space optic: MicroCarb, IASI NG, M2 mirrors of larger projects, etc… Astro instrumentationPetawatt laser optics
Safran Reosc has developped its small size robotic polish ing solutionCapacity 0-500 mmTechnology Full freeform
Glassy / SiCInterface Same for all robots
3 units recently implemented
Robotic polishing for small optics
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EUCLID M1
Journées freeform – Marseille – 12-13 Oct2017
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IBF Technology mastered since 2 decadesUSION-130 equipmentThemis solar telescope de 1-m primary (1998)
Technology scaled up for GTC 1.8-m segmentsUSION-250 equipment Installed in 2001 Used since for many large astro & space optics3 USION-150 set-up for ELT M1 segments
Technology scaled down for litho opticsUSION-30 Installed in 2005 For 35 – 350 mm aperture opticsFew mm only small footprintExtreme accuracy down to 0.3 nm RMS
Tooling preparation for handling MicroCarb opticswithin our Usion 30 equipment .
IBF finishing
27Journées freeform – Marseille – 12-13 Oct2017
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
MicroCarb focal plane is also innovativeNew Generation Panchromatic (NGP) detector from SofradirHgCdTe array hybridized on a silicon CMOS ROICBaseline of Sentinel-5 1024 x 1024 pixelsOptimized for detection from vis to 2.5-µm
Coating on sensor strongly enhances throughputAbout 40% light lost by reflection on the detector surface An AR coating on the detector strongly reduces these losses:
� Losses ≈ 15% only with monolayer� Losses < 5% with multilayer
Various developments conducted on the subjectFirst AR coating on detector in 2013 Proto 350-2500 nm AR coating in 2015Sentinel-5 space qualification in 2016
MicroCarb AR coating development in progress
Coating on the IR detector
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Image Sofradir
Journées freeform – Marseille – 12-13 Oct2017
AR coated sensor
This document and the information therein are the property of Safran. They must not be copied or communicated to a third party without the prior written authorization of Safran
MicroCarb is a high return, low cost mission1 ppm accuracy / 160 kg only / Myriades platform
Enabled thanks to: an innovative multiband spectrometer concept the use of freeform optics
Safran Reosc selected by Airbus for the supply of the optics
Efficient concurrent engineering phase for manufact urabilityDesign methodology / Freeform description / Asph amplitude / Edge margin
Preparation for polishing underway : R-SiC polishing layer selected by Airbus in place of CVDSmall size robotic polishing solution Small size IBF for extreme optical surfaces AR coating on detector
Thanks to Cnes, Airbus … and Reosc team
Conclusion
29Journées freeform – Marseille – 12-13 Oct2017