Imaging system for nanosatellite proximity operations

摘要

This paper presents a novel low-power imaging system for nanosatellite proximity operations. A robust independent camera module with on-board image processing, based on the ARM Cortex-M3 microcontroller and fast static random access memory, has been developed and characterized for the requirements of the ESTCube-1 mission. The imaging system, optimized for use in a single unit CubeSat, utilizes commercial off-the-shelf components and standard interfaces for a cost-effective reusable design. The resulting 43.3 mm ?￡ 22 mm ?￡ 44.2 mm (W?￡H?￡D) aluminium camera module weighs 30 g and consumes on the average of 118 mW of power, with peaks of 280 mW during image capture. Space qualification and stress tests have been performed. A detailed case study for the ESTCube-1 10 m tether deployment monitoring and Earth imaging mission is presented. For this purpose a 4.4 mm telecentric lens, 10 bit 640?￡480 pixel CMOS image sensor, 700 nm infrared cut-off filter and a 25% neutral density filter are used. The resolution of the assembled system is 12.7 mm and 1 km per pixel at distances of 10 m and 700 km, respectively. Custom on-board image evaluation and high dynamic range imaging algorithms for ESTCube-1 have been implemented and tested. Optical calibration of the assembled system has been performed.