<title>CCD star tracker for attitude determination and control of a satellite for a space VLBI mission</title>

In-orbit results from the attitude determination and control system of ALSAT-2B

The Aeronautical Journal ◽

10.1017/aer.2021.48 ◽

2021 ◽

pp. 1-26

Author(s):

H. Benzeniar

Keyword(s):

Control System ◽

Attitude Control ◽

Attitude Determination ◽

Lessons Learned ◽

Control Mode ◽

Star Tracker ◽

Orbit Control ◽

Space Agency ◽

Pyramidal Configuration ◽

And Control

ABSTRACT The Algerian Space Agency has been active in the field of microsatellite engineering for more than 15 years and has successfully developed microsatellites under several know-how transfer technology programs, six to date. This paper presents the flight results and lessons learned from the attitude determination and control system (ADCS) flown on the ALSAT-2B satellite, an Earth observation microsatellite, by analysing the behaviour of the satellite from the initial attitude acquisition through the coarse pointing mode then the nominal mode, where the payload is first tested, and finally the orbit control mode. The spacecraft was launched on 26 September 2016 and placed into a 670km Sun-synchronous orbit with a solar local time at an ascending node of 22:15. The ADCS performance presented here mainly focuses on the launch and early operation results. ALSAT-2B includes four reaction wheels in a pyramidal configuration, three gyros, three Sun sensors, three magneto-torquers, one magnetometer, and one star tracker for agile and accurate attitude control. In addition, a propulsion system based on four 1N hydrazine thrusters is also used on board the microsatellite. The main new development in this platform compared with previous ones of the same type is the fusion of the star tracker and measurements by the three gyroscopes into one gyrostellar estimator that was implemented for the first time on ALSAT-2B, and the pyramidal configuration of the wheels, aiming to increase the angular momentum. The results obtained from the early launch operations for different ADCS modes are very encouraging and fulfil all the requirements set during design and testing. Currently, the satellite has accomplished its fourth year in orbit and is still operational and producing high-quality images.

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Observation satellite attitude estimation using sensor measurement and image registration fusion

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410017691315 ◽

2017 ◽

Vol 232 (7) ◽

pp. 1390-1402 ◽

Cited By ~ 4

Author(s):

Zhao-Xiang Zhang ◽

Guo-Dong Xu ◽

Jia-Ning Song

Keyword(s):

Remote Sensing ◽

Image Registration ◽

Attitude Determination ◽

Simulated Data ◽

Star Tracker ◽

Remote Sensing Images ◽

Bias Drift ◽

Satellite Attitude ◽

Simulation And Experiment ◽

And Control

In order to enhance the accuracy and the robustness of the attitude determination and control system in observation satellites, a new way to fuse gyro and star tracker measurement with image registration is described. In this method, a novel and complete framework is proposed to estimate the on-orbit attitude variations from multi-spectrum remote sensing images. An extended Kalman filter is derived to calibrate the gyro bias drift and the star tracker error. The new framework is tested with realistically simulated data and remote sensing images based on JL-1 satellite. Simulation and experiment results indicate that based on the image registration, the satellite attitude variations could be detected in real time and applied for the accurate gyro and star tracker bias calibration.

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