Technologies that have been developed or extended by industry through the execution of an ESO procurement contract

Replicated diffraction gratings

The development of monolithic replicated echelle mosaic gratings at the Richardson Grating Labs was done under an initial ESO development contract and a following procurement contract. The technology was tested on a small mosaic for EMMI on the ESO 3.6m telescope, and then two larger mosaics for UVES on the VLT. Richardson Grating Labs have since delivered some 10 of these gratings to the astronomical community, including HET, SUBARU, KAO Boyhunsan, Geneva, and the Harvard-Smithsonian Center for Astrophysics MMT.

Large Glass-Ceramic Blanks

One of the most important technological hurdles for the VLT project was the manufacture of the 8 metre blanks for the primary mirrors. Mirrors of this size had never been manufactured before and several approaches were investigated by ESO (including the following example). A contract was eventually placed with Schott in Mainz for the supply of these blanks. This necessitated the creation of new manufacturing facilities at Schott and the development of their production processes to completely new dimensions. The successful completion of the VLT contract by Schott allowed them to extend and prove their technology, and puts them in a strong position to bid for future large optics.

Polishing and testing of large optical mirrors

The size of the VLT primary mirrors required a major jump in the state-of-the-art in optical manufacturing. In fact, REOSC, who received the ESO contract to polish the four 8-metre mirrors, had to build a completely new factory outside Paris for their manufacture.

The manufacturing and testing facilities developed by REOSC for the VLT were used for a subsequent contract to polish the two 8-metre mirrors for the US/UK Gemini telescope, as well as for smaller optics for other advanced projects.

Not only the size of these mirrors was unprecedented, but also the required image quality set new standards. Indeed, testing the mirror proved almost as challenging as the polishing itself. ESO worked closely with the manufacturer to produce a specification that not only fulfilled the high technical demands of the VLT project and could be verified in the factory, but also made optimum use of the VLT's Active Optics system for correcting large spatial frequency errors.

IR fibre beam combiners

A technological innovation involving optical fibres that was necessary for VINCI - the first instrument to be used with the VLT Interferometer - is the fibre-optic beam combiner. This combines and spatially filters the infrared light from two telescopes using mono-mode fibres. For this, the French firm Le Verre Fluor�as contracted to produce the high-quality IR fibre beam combiners. This firm now has almost a monopoly in this area.

Flexible mirrors

The French firm CILAS (now part of Astrium) has been responsible for supplying adaptive mirrors for all ESO AO systems. With the support of ESO contracts, they have developed two different types of actuator - the linear piezo and bi-morph - for different types of AO systems, and are currently among the market leaders in this field.

Fast tip-tilt mirrors

Fast tip-tilt mirrors are a key component of all Adaptive Optics systems and, again, the requirements are determinant for the overall system performance. With the support of an ESO development contract, the Observatoire de Paris has been developing these devices and achieved remarkable performance levels. They have supplied tip-tilt devices not only for ESO's Adaptive Optics systems, but for other projects as well such as the Gemini Telescopes.

Direct Telescope Drives

Brushless torque motors offer a number of advantages over convention telescope drive systems, including the elimination of the classical gear train (and hence mechanical simplicity) together with exceptionally good performance. Nevertheless, they had never before been used in large telescopes and nothing of the sizes required for the VLT existed in standard catalogues.

ESO commissioned a study to be carried out by the Swiss firm ETEL, and the results of this confirmed the suitability of the concept. In the VLT, direct drives from ETEL were used in the 12 Adapter/Rotators, and another specialist firm, PHASE in Italy, was contracted to design and manufacture the drives for the 4 Unit Telescopes, including the 10 m diameter azimuth drives. Since the VLT, both these firms have expanded into this market and are now among the world market leaders in this field. PHASE, for example, has recently manufactured the drives for both the 10m Gran Telescopio Canarias on La Palma, as well as for the ALMA prototype.

Visible CCDs

Ever since the first CCD detectors became available around 1980, ESO has worked closely with manufacturers to push the evolving technology in the direction that would best serve astronomy. The initial progress was both difficult and slow because of immature technology and the lack of a large commercial market to support the high development costs. A further complication is that manufacturers are unable to test the devices under the conditions in which they are used for astronomy. ESO contributed to CCD development process by a number of means. CCDs were tested in the laboratory and at the telescope and the results fed back to manufacturers. Other means were through targeted development programmes and through procurement contracts where the specifications were inevitably pushed to the limit and beyond. The characteristics that are particularly important to astronomers are good performance at cryogenic temperatures, flatness, high sensitivity from UV to NIR, very low readout noise, good cosmetic quality and often special packaging as well. For manufacturers to achieve all these things, and usually all at the same time, is challenging indeed.

Over the years, ESO has worked closely with Thomson-CSF (now Thales) in France and the UK firm E2V (previously part of the UK GEC Concern). In the 1970s, E2V for example was one of many players trying to get a foothold in the market. Today it is the world leader for supplying specialised CCDs for scientific and medical applications. Although this success cannot be accredited to ESO alone, ESO fully recognises the importance in high-tec areas of working closely with manufacturers to achieve mutually beneficial goals.

The OmegaCAM detectors comprise an array of thirty two 2k�k 4-side buttable CCDs with a total of 268 Megapixels. The ESO procurement contract with E2V specified stringent tolerances on the mechanical packaging. This was necessary to ensure that the surfaces of the individual CCDs all lay on a common image plane when mounted in the dewar. For this, E2V developed a special manufacturing technique which allows the individual CCDs to be literally "plugged in" to the dewar without any further mechanical or optical adjustment. Because of the many similar wide field applications elsewhere, this device is now a standard product.

 

 

 


ESO Technology Division
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany