title: A novel multi-aperture based sun sensor based on a fast multi-point MEANSHIFT (FMMS) algorithm.
abstract: With the current increased widespread interest in the development and applications of micro/nanosatellites, it was found that we needed to design a small high accuracy satellite attitude determination system, because the star trackers widely used in large satellites are large and heavy, and therefore not suitable for installation on micro/nanosatellites. A Sun sensor + magnetometer is proven to be a better alternative, but the conventional sun sensor has low accuracy, and cannot meet the requirements of the attitude determination systems of micro/nanosatellites, so the development of a small high accuracy sun sensor with high reliability is very significant. This paper presents a multi-aperture based sun sensor, which is composed of a micro-electro-mechanical system (MEMS) mask with 36 apertures and an active pixels sensor (APS) CMOS placed below the mask at a certain distance. A novel fast multi-point MEANSHIFT (FMMS) algorithm is proposed to improve the accuracy and reliability, the two key performance features, of an APS sun sensor. When the sunlight illuminates the sensor, a sun spot array image is formed on the APS detector. Then the sun angles can be derived by analyzing the aperture image location on the detector via the FMMS algorithm. With this system, the centroid accuracy of the sun image can reach 0.01 pixels, without increasing the weight and power consumption, even when some missing apertures and bad pixels appear on the detector due to aging of the devices and operation in a harsh space environment, while the pointing accuracy of the single-aperture sun sensor using the conventional correlation algorithm is only 0.05 pixels.
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, China. yz-dpi@mail.tsinghua.edu.cn
authors.forename: Zheng
authors.initials: Z
authors.lastname: You
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.forename: Fei
authors.initials: F
authors.lastname: Xing
authors.forename: Gao-Fei
authors.initials: GF
authors.lastname: Zhang
mesh_terms: D000465:Algorithms; D002138:Calibration; D003198:Computer Simulation; D008670:Metals / Q000737:chemistry; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D010087:Oxides / Q000737:chemistry; D012666:Semiconductors; D016082:Solar System
chemical_list: D008670:Metals; D010087:Oxides