The World's Largest Space Mirror

After two years of intensive work, EADS Astrium and BOOSTEC have successfully concluded the most important phase in the manufacturing of the largest space mirror ever produced in the world: the twelve segments that constitute the mirror have been assembled into a single part by means of a high-temperature brazing process in vacuum.

This constitutes the largest reflector (dia. 3.5 m) ever built for space applications. The Silicon Carbide Herschel telescope will weigh only 300 kg rather than the 1.5 tons required with standard technology.

This is a major step for the Herschel Telescope program, which has begun 2 years ago when EADS Astrium (Toulouse, France) as prime contractor and Boostec (Tarbes, France) as main subcontractor, were selected by the ESA to manufacture the largest space telescope ever built.

This is one of the most spectacular results of the 10 years of development undertaken in close partnership by EADS Astrium and BOOSTEC, with the unremitting support of ESA. This alliance between Europe's leading satellite specialist and a small SME with world-class know-how in technical ceramics has enabled them to bring to the space market one of the most innovative products for the coming decades: ceramics optical instruments.

HERSCHEL

The Herschel satellite is eagerly awaited by the scientific community for the new information it will provide in several astronomic areas in the submillimetric wavelength, such as the origin of the first stars and galaxies formed 12 billion years ago.

The satellite launch is planned for 2007 on the Ariane5 European launcher.

The Telescope will be placed in orbit on the second Lagrangian point, 1.2 million km from Earth and protected from light pollution from the Sun, Earth and Moon. It will work at a temperature of 70 Kelvin (-200 °C).

The Herschel telescope: A world premiere

The requirements specification of the HERSCHEL mission raised an extremely exciting challenge: to manufacture a telescope with a 3.5-m diameter, impossible using conventional technologies (glass and carbon).

Taking into account the limit on the mass to be launched and the necessary mechanical stability to guarantee accurate optical performance, from the manufacturing ambient temperature down to the cryogenic temperatures, only a few specific materials could be used for this mission. taking benefit from the experience obtained in the successful manufacturing of a brazed demonstrator 1.35 m in diameter under an ESA contract in 1999, the Silicon Carbide technology developed by EADS Astrium and Boostec was selected. The Silicon Carbide Herschel telescope will only weigh 300 kg, rather than the 1.5 tons required using standard technology.

The industrial team, structured around EADS Astrium (Toulouse, France) as prime contractor in charge of telescope design, integration and qualification, includes: - BOOSTEC (Tarbes, France) for all Silicon Carbide parts, - OPTEON (Turku, Finland) for the polishing of the reflector, - the CALAR-ALTO Observatory (Spain) for the optical coatings.

Once the final contract was signed in the summer of 2001, BOOSTEC launched a €7 m investment program to set up a unique production unit, the sole of its kind in the world, to manufacture very large Silicon Carbide parts.

A 3.5-m diameter telescope cannot be manufactured in one piece using current technology, so an assembling technique was required for the mirror's 12 segments. Considering the precisions and stabilities required for space missions, brazing the segments making up the circular reflector by means of the BRASIC® process developed by the CEA (Grenoble, France) appeared to be the most promising method.

This is the major step that was recently successfully concluded. The brazed reflector is today the world's biggest ceramic part, and the largest reflector ever built for a space application.

Now the program can move on to the next manufacturing operations whose end-result will be the final mirror. After grinding the optical face, which will down the reflector's thickness to only 3mm, the polishing phase will give the reflector its final shape and optical qualities. The process is concluded by an optical coating operation to guarantee its ultimate reflectivity. These operations will extend over 10 months, before final integration of the primary mirror into the telescope. The Herschel telescope delivery is programmed for mid-2005.

Ceramics in space: a 10-year partnership for a new product

EADS Astrium and Boostec have worked together in close collaboration for 10 years on Silicone Carbide applied to space products.

This ceramic has exceptional properties, particularly well suited to optical instruments for space applications: high stiffness, excellent heat conductivity, capability to withstand very low temperatures, low thermal expansion.

The successful integration of optical design and the material's properties have made possible "all Silicon Carbide" telescopes which are lightweight and have excellent thermal uniformity.

This technological breakthrough has produced direct benefits on mirror weight (generally speaking, 5 times lighter than the glass equivalent), but also simplified telescope structures.

This technology has already been used for instruments such as the Earth observation satellite Rocsat 2 (Taiwan) to be launched in January 2004 and Osiris, an instrument on board Rosetta (ESA) whose launch is programmed for February 2004.

In parallel to Herschel, another instrument is being manufactured: Aladin (Atmospheric Laser Doppler Lidar Instrument), to be mounted on the ESA's AEOLUS satellite.

In the field of further applications, the Japan Aerospace Exploration Agency (JAXA) has signed a study phase contract with EADS Astrium for the design of the Silicone Carbide telescope for the new infrared observatory named SPICA. This satellite will work in a shorter wavelength range than Herschel, thus providing better performances.

EADS Astrium

EADS Astrium is Europe's leading satellite specialist. Its activities cover civil and military telecommunications and Earth observation systems, science and navigation programs, and all spacecraft avionics and equipment.

EADS Astrium is wholly owned by EADS SPACE. In 2002, EADS SPACE had a turnover of €2.2 billion and 12,300 employees in France, Germany, the United Kingdom and Spain.

Press contact: EADS SPACE (FR) Rémi ROLAND +33 (0) 1 34 88 35 78 EADS SPACE (UK) Alistair SCOTT +44 (0) 1438 77 3698 EADS SPACE (GER) Mathias PIKELJ +49 (0) 7545 8 91 23 www.space.eads.net

BOOSTEC

BOOSTEC is a young spin-off created in 1999 by an experienced research and development team.

BOOSTEC is the world's sole manufacturer of sintered silicon carbide mirrors and telescopes. Its partnership with EADS Astrium makes it a key player on the European market.

Its initial phase over, BOOSTEC now has the skills, equipment and contracts to develop an annual turnover of €5 to 6 million in optical instruments. Its workforce currently numbers 30 people.

BOOSTEC's main shareholders are:

• Pierre DENY and Anne PAIN, the company directors (69%),
• IRDI, the biggest venture capital company of the Midi-Pyrénées Region (15.5%),
• EADS Astrium (15.5%)