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Many satellite-borne measurement applications require lightweight, reflective near diffraction limited telescopes with wide spectral bands (UV/visible to LWIR), for operation in space environments and over wide temperature ranges. Emerging silicon carbide (SiC) technology provides an attractive material for these telescope applications. It offers (1) the lightweight and stiffness of beryllium, (2) the diffraction limited visible optical performance of glass, (3) superior thermal stability to cryogenic temperatures, and (4) the cost and rapid fabrication advantages of aluminum. This paper describes the design, development, and test for a 50 cm dia. aperture on-axis imaging SiC telescope, and a 'goes like' 0.5 multiplied by 0.3 m scan flat for a geo-stationary earth observatory (GEO) mission. Optical, thermal, and structural design and analyses are described for the demonstration hardware. The scan mirror and telescope system have been optically tested over the temperature range of plus or minus 50 degrees Celsius. Temperature gradients have been induced on the scan mirror and telescope simulating non uniform thermal loading from the earth and sun. Test results are presented which show the excellent optical/thermal stability properties of SiC. |
