Optical Glass ProductionADVANCED and QA OPTICS Glass Ceramic ZERODUR® for Space Application

Peter Hartmann, Thorsten Döhring, Martin Schaefer, SCHOTT AG Mainz

The zero expansion glass ceramic ZERODUR from SCHOTT is widely used for earth bound precision mirror and support structure applications. This poster shows that it is also suited for space applications. Recent developments show that high light weighting degrees are possible saving mass to be launched and that such structures are strong enough to survive launch vibrations. A series of reference applications, where Zerodur has been and is being used (ROSAT, CHANDRA, Meteosat SEVIRI, Hubble Space telescope,…) demonstrate the high and long lasting performance of Zerodur components and thus continuously enlarges the space heritage of the material.

ZERODUR® in Space: List of Successful Applications

SPOT Earth Observation Satellites Weather Satellites Space Observation Satellites

Dimensions Weight Launch/ Dimensions Weight Launch/ Dimensions Weight Launch/ Project Orbit Project Orbit Project Orbit ø/mm Reduction Duration ø/mm Reduction Duration ø/mm Reduction Duration 2.7.1985 – 22.2.1986 – Meteosat 2.3.1991 - Giotto 250 x 30 - Comet Halley SPOT 1 735 x 85 70 % 832 km 400 x 45 65 % 36.000 km 23.7.1992 31.12.1990 5 26.4.2007 Hipparcos 8.8.1989 – 22.1.1990 Meteosat 20.11.1993 till 600 x 70 70 % Elliptic SPOT 2 735 x 85 70 % 832 km 400 x 45 65 % 36.000 km Astrometry 6.1993 till now 6 now 884 x 583 to 8 conic 26.9.1993 – Meteosat 3.9.1997 till ROSAT 580 km 1990 - 1999 SPOT 3 735 x 85 70 % 832 km 400 x 45 65 % 36.000 km 470 x 583 tubes 14.11.1997 7 now MSG-1 24.4.1990 to 24.3.1998 530 x 830 73* Geostationary 28.8.2002 Hubble M2 300 Solid 569 km SPOT 4 735 x 85 70 % 832 km Meteosat now till now (elliptic) 35600 km Till now 8 Elliptical MSG-2 CHANDRA 1225 x 991 to 12 conic extrentric 63.5 h 23.7.1999 to 4.5.2002 530 x 830 73* Geostationary 21.12.2005 SPOT 5 735 x 85 70 % 832 km Meteosat (AXAF) 632 x 991 tubes 10000 – 140000 now till now (elliptic) 9 35600 km Till now km

Picture:SAGEM-REOSC Picture: Carl Zeiss

X-Ray Satellite ROSAT Hubble Space Telescope

„ ZERODUR-Mirrors „ 4 x 2 Mirror Elements 0.85 m wide max x 0.5 m long „ Super polish: 0.2 nm „ Resolution: 2.4 arcsec in 0.1 – 2 keV Pictures: NASA in 0.04 – 0.2 keV „ In orbit 1.6.1990 to 12.2.1999 The secondary mirror is a 308 mm x 65 mm Picture: Carl Zeiss „ Altitude 580 km almost circular ZERODUR Mirror 12.3 kg convex hyperboloid 1.36 m radius

X-Ray Satellite CHANDRA (formerly AXAF)

X-Ray telescope with best image resolution M. Weisskopf, NASA priv comm.: Key element: Wolter telescope - hollow conical cylinders In almost 10 years of on-orbit made from ZERODUR performance (Launch July 23, 1999), „ ZERODUR-Mirrors we have seen no degradation „ 4 x 2 Mirror Elements in the point source response function. 1.2 m wide max x 1 m long „ Super polish: 0.2 nm „ Resolution: 0.5 arcsec in 0.2 – 10 keV „ In orbit since 1999 Delivery 1989 -1991 Picture: „ Altitude 10000 – 140000 km Pictures: NASA NASA Picture: NASA

Significant Progress in Light-Weighting of ZERODUR at SCHOTT Two different ways lead to light/weighting degrees > 90 %

Grinding and subsequent acid etching Advanced Grinding Rib thickness 2 mm Structure Optimization with respect Rib height 190 mm to stiffness and print through via FEA Curved bottom

ƒ Ground to 2,5 mm thickness Etched to 0,65 mm thickness

New Data on the Strength of ZERODUR Planned Space Applications

D151 / D64 Ground and Etched Samples LISA Pathfinder – LISA Technology Package

4 Sample # 7 N = 67 Sample # 5 N = 138 LISA – The Laser Interferometer D64 Ground D151 Ground Inertial sensors 22 kg each & etched 73 µm Space Antenna Project of NASA / Dimensio Weight Launch/ 2 σc 54.1 λ 28.2 Supported only by ZERODUR structures 99% σc 303.1 λ 4.5 Project Orbit

ln ln (1/(1-F)) ns ø/mm Reduction Duration 90% ESA 0 63% Assembled system of inertial Jumbo Jet 50% Sample # 2 N = 131 The Keck Telescopes at the The Keck Telescopes at the 2705 x D64 Ground SOFIA 75 % 14 km 2009 20% Hawaiian Mauna Kea Summit sensors held by ZERODUR Hawaiian Mauna Kea Summit 350 -2 Data 2008 10% Stratosphere σc 62.8 λ 11.0 structures 5% Sample # 8 N = 63 Special D151 Ground SILEX 280 x 400 LEO & GEO 2010 -4 2% & etched 181 µm Structure 1% Successfully tested with 15 g σc 497.2 λ 3.4 0.5% Sample # 6 N = 39 sine and 18 g random vibrations MSG-3 / 530 x 830 Geostat. 2011/ -6 D64 Ground 73* 0.2% & etched 91 µm 4 (elliptic) 35600 km 2013 0.1% σ 391.4 λ 3.0 c Æ Major step forward in the -8 1020 30 40 5060 70 100 200 300 400 Stress [MPa] 1000 LISA Pathfinder mission Even in ground state Zerodur is comparatively strong With etching the strength can be increased significantly Picture: EADS/ASTRIUM Picture: ESA/ NASA

DGaO-Proceedings 2009 - http://www.dgao-proceedings.de - ISSN: 1614-8436 Poster P62 – 2009 Brescia Italy