Satellite equipment supplier invests in beam expanders

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Tesat-Spacecom, based in Backnang, Germany, is using a thermally-stabilised beam expander from Optical Surfaces as part of its Tesat Optical System Test Bed for verification of the optical performance of its laser communication terminals (LCTs).

Tesat-Spacecom is a global designer and manufacturer of payload equipment for communication satellites. Tesat LCTs are the result of more than two decades of development expertise in the field of optical communications, and Tesat's broad knowledge of space systems production. The US Missile Defence Agency's NFIRE satellite, built by General Dynamics, and Germany's TerraSAR-X satellite, both launched in mid-2007, each carry a Tesat LCT. This equipment enables point-to-point data transfers with high data volume. With a range of 45,000km and a transfer rate of more than 5 Gigabit per second, this technology is revolutionary and communication via laser allows a 10-times higher data rate, compared to a usual microwave link.

Reflecting on the choice of supplier, Dr Andreas Weichert, responsible for the Tesat Optical System Test Bed, commented: 'Optical Surfaces was selected to produce the critical 10x beam expander for our Optical System Test Bed, because of their impressive track record in preparing high performance optical systems for telescope and space projects. We were also very pleased with a previous beam expander supplied by Optical Surfaces in 2006'.

Using proprietary production techniques, Optical Surfaces will produce two concave off-axis parabolic mirrors, with a combined wavefront accuracy of lambda/35 rms, that form the principal optical elements of the common focus 10x beam expander. The excellent surface accuracy achieved during manufacturing will enable the beam expander to provide sustained high optical performance over the complete field of view (+/- 0.1 degrees at large aperture). Manufactured in INVAR - the beam expander was designed be used in vacuum at 10-6 mbar and offers high thermal stability for thermal gradients that may be as much as 10°C along the length of the instrument.