Extensible Boom-Based Optical System for Nano-Scale Remote Sensing Satellite PRISM

Intelligent Space Systems Laboratory (ISSL), the University of Tokyo is now developing the nano-scale remote sensing satellite named as PRISM. This satellite aims at obtaining high resolution Earth images with 30m of ground resolution. Conventional remote sensing satellites have adopted reflective optical system using multiple mirrors to realize long focal length and large aperture. However, such system requires very high stiffness, machining accuracy and thermal management in order to maintain the designed light path. Thus we concluded that common reflective optical system cannot be applied to our nano-satellite, and adopted a totally different concept. PRISM deploys an extensible boom up to 800mm in space. The boom has a lens on its end, which realizes the desired long focal length. In other words, the boom works as a structure of telescope. Of course additional technological issues occur if we employ this methodology, such as how to keep focusing at the focal plane, and how to avoid the stray light coming into the optics. We are developing a kind of auto-focus system suitable for our nano-sized satellite, and light shade to be implemented on the extensible boom. PRISM is now at the engineering model phase, intending to be launched in 2006