Development of the TopSat camera

The TopSat camera is a low cost remote sensing imager capable of producing 2.5 metre resolution panchromatic imagery, funded by the British National Space Centre’s Mosaic programme. An engineering model development programme verified optical alignment techniques and crucially, demonstrated structural stability through vibration tests. As a result of this, the flight model camera has been assembled at the Space Science & Technology Department of CCLRC's Rutherford Appleton Laboratory in the UK, in preparation for launch in 2005. The camera has been designed to be compact and lightweight so that it may be flown on a low cost mini-satellite (~120kg launch mass). To achieve this, the camera utilises an off-axis three mirror anastigmatic (TMA) system, which has the advantages of excellent image quality over a wide field of view, combined with a compactness that makes its overall dimensions smaller than its focal length. Keeping the costs to a minimum has been a major design driver in the development of this camera. The camera is part of the TopSat mission, which is a collaboration between four UK organisations; RAL (Rutherford Appleton Laboratory), SSTL (Surrey Satellite Technology Ltd.), QinetiQ and Infoterra. Its objective is to demonstrate provision of rapid response high-resolution imagery to fixed and mobile ground stations using a low cost mini-satellite. This paper describes the opto-mechanical design, assembly and alignment techniques implemented and reports on the test results obtained to date.