Attitude Stabilization of Spacecraft in Very Low Earth Orbit by Center-Of-Mass Shifting

Abstract

At very low orbital altitudes ( 450 km) the aerodynamic forces can become major attitude disturbances. Certain missions that would benefit from a very low operational altitude require stable attitudes. The use of internal shifting masses, actively shifting the location of the spacecraft center-of-mass, thus modulating, in direction and magnitude, the aerodynamic torques, is here proposed as a method to reject these aerodynamic disturbances. A reduced one degree-of-freedom model is first used to evaluate the disturbance rejection capabilities of the method with respect to multiple system parameters (shifting mass, shifting range, vehicle size, and altitude). This analysis shows that small shifting masses and limited shifting ranges suffice if the nominal center-of-mass is relatively close to the estimated center-of-pressure. These results are confirmed when the analysis is extended to a full three rotational degrees-of-freedom model. The use of a quaternion feedback controller to detumble a spacecraft operating at very low altitudes is also explored. The analysis and numerical simulations are conducted using a nonlinear dynamic model that includes the full effects of the shifting masses, a realistic atmospheric model, and uncertain spacecraft aerodynamic properties. Finally, a practical implementation on a 3U CubeSat using commercial-off-the-shelf components is briefly presented, demonstrating the implementation feasibility of the proposed method.

Satellite Communications in the New Space Era: A Survey and Future Challenges

“…However, such low altitudes contain a denser part of the atmosphere, and therefore, larger aerodynamic forces. This can be seen as a challenge, but they can also represent an opportunity for orbit and attitude control [17]. Moreover, the increased drag represents a shortening of the orbital lifetime, but this also means a more frequent fleet replacement of smaller and cheaper spacecrafts, thus, becoming more responsive to technology and market changes [18].…”

Speed-adaptive dynamic surface attitude control for a satellite with moving masses under input constraints

“…Remark 1: The atmospheric environment is variable and poorly predictable, and spacecraft aerodynamics are not particularly well understood (Virgili-Llop et al, 2019). In LEO, the environmental force F e can be simplified to be the ideal aerodynamic force F aero with unknown errors in magnitude and direction.…”

The Benefits of Very Low Earth Orbit for Earth Observation Missions

“…Passive aerodynamic stabilisation or aerostability (the pointing of a spacecraft in the direction of the oncoming flow) has been demonstrated in orbit by several missions [6,71,72], whilst further aerodynamic attitude control concepts including use of external surfaces to perform detumbling [73], internal momentum management [74], and pointing manoeuvres [75][76][77][78] have also been considered. Centre-of-mass shifting has also been proposed as a method to augment aerodynamic stabilisation [79,80].…”