All SiC telescope technology at
EADS-Astrium
Jacques Breysse / Didier Castel : Astrium
Michel Bougoin : Boostec
ICSO 2012
Summary
 Silicon Carbide
 Short history
 SiC Properties
 Application and developments
 Conclusion
Date - 2
Silicon Carbide : short history
 SiC optics development started at ASTRIUM(1) in the early ninety’s.
 During 10 years, ASTRIUM and BOOSTEC have funded R&T activities for
developing optimised processes for space optics manufacturing.
 The complete design and manufacturing chain is now perfectly controlled and
mastered by ASTRIUM/ BOOSTEC-MERSEN up to Ø4 m
 Recently, BOOSTEC joined MERSEN(2) group.
 Mersen group brings strong reinforcement of Boostec on two key topics
 The world largest isostatic presses are now available in 2 Mersen plants
located in the United-States and in China
 Ф1.5 m SiC CVD furnaces are available in Mersen Gennevilliers, near Paris
(and also in the United-States)
(1) formerly
Matra Espace
(2) formerly Carbone Lorraine
Date - 3
Sintered SiC properties
 ITAR free (Full European source from powder
to final product)
100
 Insensitive to space radiations:

no degradation for 200Mrad ( rays)
90
Boostec SiC
Zerodur
 Insensitive to hard chemical attacks (inert)
 No outgassing / No humidity effect
 Extreme temperature range:

O K à 1800 K
 Can be polished at high level optical
quality level

Excellent specularity with SiC CVD (CVD
Steady state stability ( )
 No ageing effects/No residual stresses
80
70
HB CeSiC
CeSiC
60
50
ULE
AlN
40
30
Si3 N4
Beryllium
20
Alu 6061
10
cladding has same CTE of S-SiC )

Optical coating can be applied easily
 Existing industrial facilities for very
large pieces (up to 4 m)
 Space qualified assembly techniques
(Gluing,Bolting,brasing)
0
0
20
40
Polishable material
60
80
100
120
Specific rigidity (E/)
140
160
180
200
Interest for space application
 The use of the same material for the telescope structure and mirrors provides unprecedented
development advantages




Reduced number of elementary pieces and interfaces, design robustness,
Reduced number of materials and processes, quality control aspects
Excellent and accurate mathematical modelling:
Both Structural and mirrors can be assembled in a homogeneous telescope and optical instrument
 All SiC telescope refocusing capacity
 A separate thermal control of a telescope mirror wrt telescope structure offers an efficient and reliable
refocusing capacity for free
 Already implemented on ASTRIUM Earth Observation payloads but, up to now, no need to be used in
orbit (telescope performances are as measured on ground and without instability)
 Example Formosat-2,THEOS,NAOMI product line
 Formosat 2 main test results
 3µm short term defocus variation : as expected through thermal prediction
 Excellent correlation with thermal model (temperature and gradients)
 Thermal re-focalisation range +/- 200µm by heating M1 (+/- 6°C)
200
150
Calculated Focus from temperatures
-6K
+6K
100
Measured Focus (PAN 6002)
Monitoring T° : mirrors
M1
50
- 110 µm
+ 110 µm
(µm)
M2+ structure
24
+ 5K
Phase 1
T° (°C)
M1 temp. control
+6K
20
- 5K
- 6K
-6K
Structure temp. control
18
16
0
+ 5K
22
- 200 µm
-50
-100
+ 200 µm
-5K
-150
+5K
14
-200
12
10
04/11/2002 00:00
04/11/2002 06:00
04/11/2002 12:00
04/11/2002 18:00
+ 90 µm
- 90 µm
-5K
Page 5
+5K
Phase 3
Phase 5
Phase 7
Phase 9
Phase 13
Herschel telescope
 Main characteristics




All SiC Telescope completely (M1, M2 mirrors, barrels, hexapod)
Primary mirror Ø 3,5m ; F/0,5
Mass:260 Kg
Areal density: 27 kg/m²
World larger telescope manufactured
in ceramic
material
 Performances
 Operating temperature : 70K
 WFE < 6µm rms,
within the [80 µm, 670µm] spectral band
 M= 300Kg Fq lat: 45Hz, Fq longi: 87Hz
 M1 mirror manufacturing process:
 Assembly and brazing of 12 segments
 Circular machining of the assembled mirror
 Polishing, rugosity = 30 nm rms, Al treatment
 Status
 Launched in 2009
 High and stable performances exhibited in-orbit
AEOLUS / ALADIN
 Lidar Mission for global measurement of vertical wind profiles
 Wind Measurement Performances
 1-2 m/s accuracy until 20 km height
 Measurement capability up to 30 km
 UV beam from Nd:YAG laser 100 mJ per 25 ns shot @ 50 Hz
 Telescop Characteristics
 1.5 m diameter SiC telescope
 Mass: 63 kg
 Primary mirror :
 Mass 47 kg
 Areal density:27kg/m²
 WFE: 150nm RMS
Aladin instrument
Telescope
Gaia, a mission for Astrometry(1)
 Main instrument features
 Telescopes
 2 telescopes separated by 106,5 deg
 1,45 x 0,5 m² pupils, 35 m focal length
 10 mirrors , overall WFE < 50 nm
 Silicon Carbide stable structures
 Ø3m torus : 19 brazed parts
 0.1 mK thermal control
 Basic Angle stability < 35 picorad over 6 hours
Focal PlaneAssembly
 Focal Plane Assembly & Processing
 106 CCD detectors, 4500 TDI, cooled at 160K
 Autonomous star detection (10 000 obj/s)
 Measure of star PSF (Astro) and spectra
(RVS, blue & red photometers)
 7 Video Processors : HW-SW architecture
with 1 Gips processors @ 630MHz
 PLM delivery beg.2013
 FPA Vibrations passed, delivery in Apr.2012
 PLM Vibrations & TV tests in Aug.-Dec.2012
Torus, bipods and all optics aligned
Gaia, a mission for astrometry(2)
M1 mirror at Sagem WFE=17nm rms
3m torus during telescope
Alignment
RVS spectrometer with 200x200 mm
prismatic lens and binary grating
Blue photometer
SG Apr. 2011
BAM
interferometer,
TNO
Folder Optical Structure
(FOS)
NIRSpec payload(1)
 NIRSpec : a JWST payload

The Near InfraRed Spectrograph (NIRSpec) will operate over a
wavelength range of 0.6 to 5 microns.

The spectrograph has multi object capability thanks cryogenic
microshutter system
 Operating temperature: 35 K
 Structures and mirrors are in S-SiC
 Total mass: 185 kg
10
Technologie SiC : 14 décembre 2005
All the grey parts are
made with Sintered SiC
(Mirrors + Structures)
NIRSpec payload(2)
All SiC TMAs
21/11/2012
Multi spectral instruments:
Sentinel 2 MSI & Ocean Color Imager
MSI
Performances

13 spectral bands:0.4 µm - 2.4 µm

Swath: 290 km

Resolution: 10 m - 60 m

150 mm effective pupil diameter full Sic Off-Axis
TMA telescope (20.6°FoV and l/10 optical quality)

2 focal planes
Instrument Characteristics

VNIR focal plane populated with 12 detectors

SWIR cold focal plane populated with 12 detectors
OCI operating from GEO Orbit
Main features
 All SiC TMA telescope and Focal plane based on dedicated
Advanced 2 Mpixels CMOS Detector
 Pointing Mechanism allowing 2500 x 2500 km2 area
scanning in 16 slots in less than 30 minutes, with an
average resolution of 500 m (< 360 m NADIR)
 Images in 8 narrow spectral bands in the [400 nm - 800 nm]
range thanks to 8 filters
 Launched :2010
FORMOSAT 2 & THEOS CAMERAS
13

GSD: 2.0 m

Swath width: 24 km

Cassegrain Telescope with field corrector in “Horizontal
position”

Primary mirror : 600 mm

Telescope optical quality: (WFE)< 40 nm

Instrument Mass: 100 Kg + 22 kg (electronics)

Launched

FORMOSAT 2 : 2004

THEOS: 2008
Technologie SiC : 14 décembre 2005
NAOMI Family Remote sensing Camera (1)
 Naomi SiC cameras  200 mm
Spot 6 Cameras
 Full SiC instrument / telescope
(mirrors, optical bench, structure)
 Robust to sun pointing
 Simple thermal control
 Korsch optical design can be adapted to
several missions


Swath: from 10 km to 30 km
GSD: from 2,5 m to 1,2 m
8 Cameras have been developed and space qualified
( 4 already fly and work perfectly and 4 will be launched next year)
19 kg /  200 mm
NAOMI Family Remote sensing Camera (2)
NAOMI Sic Cammera  650 mm
 GSD PAN @ Nadir: 1 m
 GSD XS @ Nadir: 4 m
 Swath > 20 km
Characteristics
 Korsch optical configuration in « Vertical Position »
 Pupil diameter: 650 mm
 Mass: 130 kg (camera) + 20 kg (video electronics)
 Optical Camera status
 Delivered to satellite :February 2013
 Launched : 1 S 2014
SiC main structure
during integration
650 mm primary
mirror during
polishing @SAGEM
Conclusion: EADS-Astrium Silicon Carbide
technology
1993
1996
Brazed mirror
Large SiC piece
 0,63 m
1.2m x 0.43 m
1990
Beginning of SiC
R&D activities
1998
SOFIA- M2  0,35m
2002 & 2007
2006
2008
ROCSAT 2 & THEOS
Aladin Telescope
Cameras  0,6 m
 1,5 m
GOCI camera
 0,2 m
2000
1990
Osiris camera
 0.15 m
1999
flat mirror
Fisrt BB Ø
1.35m
0,72 m x 0,35m
1997
All SiC bi–telescope
SiC technology
R&D activities
2012
GAIA
Sentinel 2
2005
2000
1994
2008-2012
2002
Mirror  1 m
2012
2006
2007
2007
Herschel Telescope
Gaia off-axis Mirror
 3,5 m - 12 segments
1.5 m x 0.5 m
ELSA Airborne
optical terminal
ATLID
NIRSPEC
2009 - 2013
NAOMI
Today
 9 full SiC instrument in orbit and,
 9 full SiC instrument ground qualified or under development
Conclusion
 The SiC material is an unique material for space optics
 Both mirrors and structures are built with the same material leading to very large, lightweight and stable
telescopes operating over a very large range of temperatures
 The SiC manufacturing process is efficient ,fast and affordable. SiC export cameras
are routinely developed in less than 24 months.
 Thanks to BOOSTEC skill and expertise, the main advantage of ASTRIUM/BOOSTEC SiC is related to the
fast blank mirror and structure machining and light weighing.
 The SiC manufacturing process is much more efficient and much less risky than any other optical
technology
 Optimised polishing techniques have been developed in the recent years leading to very high optical
quality mirrors
 This technology spans a very large space optical applications
 From the very cost effective remote sensing Naomi camera
 To the huge scientific telescope working at cryogenic temperature as Herschel , GAIA and NIRSPEC
 18 space qualified instruments have been developed in the past 10 years
 More than 150 SiC mirrors and structural parts have already been manufactured for space applications.
 9 instruments are already in orbit and satisfactorily work
 9 instruments will be launched in the coming years
 During Recent years Space and Optical community (US,Japan, India and China) pay
a great interest to Silicon Carbide technology
 Almost all developed countries (Eastern and Western) invest in this technology to develop large optical
payloads and focal planes.
Date - 17