Effect of aerodynamics drag and radiation pressure on orbit and attitude dynamics coupling of small spacecraft
Abstract
Accurate orbit modeling and high fidelity prediction of spacecraft behavior under external forces and torques are essential to mission success. The equations of motion in astrodynamics are complex nonlinear, coupled, differential equations that have resisted direct solution. Throughout the years, several hypotheses and simplifications have been applied to obtain an analytical solution to the problem. However, modern computers allow us to use numerical techniques to integrate the equation of motion in their complete form. Most of the orbital propagators decoupled the orbital dynamics from the attitude dynamics so as to alleviate the computational effort to fully integrate the general attitude -orbit problem. They assume that the fundamental frequency of the orbital motion is much smaller than the attitude dynamics. Hence, they usually use averaged parameters over one revolution to account for atmospheric and radiation effects or even neglect them in specific cases. Aerodynamics drag and radiation pressure forces, contrary to the gravity force, depend directly on the spacecraft orientation and may have a substantial impact on the spacecraft trajectory. Nowadays, nanosatellites have become more popular due to their low-cost to build and launch into space. However, since most of the current nanosatellites do not have actuators for orbit control due to their complexity and limitations in space, they cannot counteract the external perturbing forces, such as drag and radiation pressure. These perturbing forces modify the spacecraft trajectory and they depend on the orientation. For this reason, a fully coupled attitude-orbit model is needed to study how the nominal orbit is perturbed. The aim of this paper is to investigate the effects of both forces on the orbital-attitude coupled problem focused on nanosatellites in LEO orbits. This paper focuses on near-circular LEO orbits since most of the current nanosatellites are put into similar orbits. The model uses a Keplerian two body gravity model along with aerodynamic and radiation pressure forces. More complex gravity models, third body perturbations or other non-gravitational perturbations are not accounted for. The radiation pressure forces include solar radiation, albedo radiation and earth planetary radiation. The geometry of the spacecraft is modeled as a collection of flat plates with uniform material properties.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E2339A