In-orbit performance of Attitude Control System in DubaiSat-2

摘要

The Dubaisat-2 is a 1-m resolution remote sensing satellite system developed jointly by Satrec Initiative and Muhammed Bin Rashid Space Centre of UAE and it is fully operational since its successful launch on November 2013. The primary mission objectives are to provide high resolution images of earth observation. This paper represents the attitude control performance of Dubaisat-2 in space focusing on the launch & early operation results. The Dubaisat-2 has implemented reaction wheels, gyros, star trackers, sun sensors, magnetometers and magnetic torquer for agile and accurate attitude control purposes. The attitude control hardware and flight control software support various operations and maneuvers for efficient and advanced imaging missions. The required attitude pointing accuracy of 0.12 deg (3 sigma) and the stability of 0.009 deg/sec (3 sigma) are verified by in-orbit performance analysis. For 3-axis attitude control and stabilization of a rigid spacecraft, quaternion feedback law is applied in Dubaisat-2 and settling time to set PD gain is auto-scheduled in on-board software. The conservative pyramidal configuration of four reaction wheel and additional one reaction wheel is applied and continuous wheel momentum dumping is performed by using magnetic torquer. The control torque distribution optimization is based on a null space solution. Dubaisat-2 is designed to support the imaging functions such as single, multi strip and single-pass stereo imaging. For the geometric and radiometric calibration, stars and moon imaging operations are also performed for value-added image product. In this paper, the overview of the DubaiSat-2 attitude control system is described with focusing on the launch & early operation results. Lessons learned from flying experiences and analysis results will contributes to sustainable development in Satrec Initiative.