Coupled orbitattitude dynamics and relative state estimation of spacecraft near small Solar System bodies
Abstract
The effects of dynamical coupling between the rotational (attitude) and translational (orbital) motion of spacecraft near small Solar System bodies is investigated. This coupling arises due to the weak gravity of these bodies, as well as solar radiation pressure. The traditional approach assumes a pointmass spacecraft model to describe the translational motion of the spacecraft, while the attitude motion is considered to be completely decoupled from the translational motion. The model used here to describe the rigidbody spacecraft dynamics includes the nonuniform rotating gravity field of the small body up to second degree and order along with the attitude dependent terms, solar tide, and solar radiation pressure. This model shows that the second degree and order gravity terms due to the small body affect the dynamics of the spacecraft to the same extent as the orbitattitude coupling due to the primary gravity (zeroth order) term. Variational integrators are used to simulate the dynamics of both the rigid spacecraft and the point mass. The small bodies considered here are modeled after NearEarth Objects (NEO) 101955 Bennu, and 25143 Itokawa, and are assumed to be triaxial ellipsoids with uniform density. Differences in the numerically obtained trajectories of a rigid spacecraft and a point mass are then compared, to illustrate the impact of the orbitattitude coupling on spacecraft dynamics in proximity of small bodies. Possible implications on the performance of modelbased spacecraft control and on the stationkeeping budget, if the orbitattitude coupling is not accounted for in the model of the dynamics, are also discussed. An almost globally asymptotically stable motion estimation scheme based solely on visual/optical feedback that estimates the relative motion of the asteroid with respect to the spacecraft is also obtained. This estimation scheme does not require a model of the dynamics of the asteroid, which makes it perfectly suited for asteroids whose properties are not well known.
 Publication:

Advances in Space Research
 Pub Date:
 April 2016
 DOI:
 10.1016/j.asr.2015.05.023
 Bibcode:
 2016AdSpR..57.1747M
 Keywords:

 Orbitattitude coupling;
 Relative pose estimation;
 Small bodies