Design, Analysis and Testing of a Novel Deployable Telescope for Earth Observation using Small Satellites

摘要

The Surrey Space Centre (SSC) and Surrey Satellite Technology Ltd (SSTL) have collaborated in a Centre for Earth Observation Instrumentation (CEOI) sponsored project to design a deployable Cassegrain telescope. Deployable structures have proved very successful in the past decades for deployment of sensors and solar panels, to name a few. Therefore, attention has naturally turned to incorporating deployable structures into more complex space systems. Optical telescopes are currently flown with a fixed focal length, set by the desired magnification, which limits their use to larger satellites. Incorporating a deployable system, to extend to the fixed length from a smaller volume, could open the door for smaller satellites to carry larger optical telescopes, making Earth observation more accessible for research and businesses. The aim of this project was to increase the capability of small satellites for Earth observation by demonstrating a proof of concept breadboard and development model of a deployable Cassegrain telescope. The design uses three concentric carbon fibre barrels deployed into lockout stops by three leadscrew sets equi-spaced around the barrels. This paper will provide an overview of the design, analysis and test campaign for this deployable optical system. Demonstration and validation of the design was completed on two fronts, analysis and test. The requirements can be simplified to deployment repeatability, structural performance and thermal stability. The deployment repeatability was physically tested using an aluminium test rig and suspended digital test indicators. The structural performance was first modelled using finite element (FE) software then experimentally using a suspended mini-shaker. Finally, the thermal stability of the system was investigated using FE and validated experimentally, using an autocollimator, reference tube and thermal chamber. The deployment results for both the development model show that the system can reliably deploy