Drag-free controller design of the ultra-low-orbital flight

The ultra-low orbit satellites generally orbit at an altitude about 200 km, and have better performance of observing the Earth and receiving information while using the same observation instrument, thus have good economic benefits and broad application prospects. However, the aerodynamic forces and moments interference to the ultra-low-orbit satellites are dozens of orders of magnitude higher than to the traditional ones, resulting in a serious disturbance on the satellites´ states, like orbits decay and strong attitude and orbit coupling phenomena. The drag-free controller must meet certain requirements of the power spectral density (referred to as PSD), and the attitude and orbit control power consumption must be economized as low as possible. This paper focus on the accurate atmospheric modeling at 200 km, studies the atmospheric disturbance on the orbit and attitude performance of the low- orbit satellite; compensates the atmospheric perturbation on the orbit and attitude by using the drag-free technology; achieves precise control of low-orbit satellite orbit and attitude by means of three control loop: the test mass loop, the satellite body loop and satellite-test mass loop; besides, in order to improve the control precision, there used the Embedded control strategy considering the measurement noise, the estimated impact of noise, the interference noise and other unknown perturbations. Finally, the paper design appropriate orbital parameters observer and estimator so as to match the attitude and orbit control loop´s input. Aerodynamic drag can be used to control the satellite attitude to save energy through rational design, this work try to verify the feasibility of the use of aerodynamic drag for auxiliary attitude control.