Aaron J. Rosengren, (University of Colorado), Daniel J. Scheeres (University of Colorado)
Keywords: Orbital Debris
Abstract:
The high area-to-mass ratio (HAMR) debris population is thought to have origins in the GEO region. Many of these objects are uncharacterized with apparent area-to-mass ratios of up to 30 meters squared per kilogram. The orbits of HAMR objects are highly perturbed due to the combined effect of solar radiation pressure (SRP), anomalies of the Earth gravitational field, and third-body gravitational interactions induced by the Sun and the Moon. A sound understanding of their nature, orbital evolution, and possible origin is critical for space situational awareness. The study of the orbital evolution of HAMR objects, taking into account both short-period and long-period terms, requires numerical integration of the precise set of differential equations, and the investigation of a broad range of possible parameter values. However, such computations become very costly when continuously applied over a period of several decades, as is necessary in the case of HAMR debris. It therefore seems reasonable to investigate the equations that govern the long-term behavior of orbits; such equations can be derived by the method of averaging. We have validated a semi-analytical averaged theory of HAMR object orbit evolution against high precision numerical integrations, and are able to capture the extreme dynamical behaviors reported for these objects. This new averaged model, explicitly given in terms of the eccentricity and angular momentum vectors, is several hundred times faster to numerically integrate than the non-averaged Newtonian counterpart, and provides a very accurate description of the long-term behavior. Using this model, it is possible to make predictions of how a population of HAMR objects, released into GEO orbit, will evolve over time. Our earlier analyses revealed that the population would have a range of orbits much different than circular GEO. Their orbits will suffer a sub-yearly oscillation in the eccentricity and inclination evolutions, and a longer-term drift in inclination. When the nodal rate of the system is commensurate with the nodal rate of the Moon, the perturbations build up more effectively over long periods to produce significant effects on the orbit. Such resonances, which occurs for a class of HAMR objects that are not cleared out of orbit, gives rise to strongly changing dynamics over longer time periods. In this paper, we present the averaged model, and discuss its fundamental predictions and comparisons with explicit long-term numerical integrations of HAMR objects in GEO space. Using this tool, we study a range of HAMR objects, released in geostationary orbit, with various area-to-mass ratios, and predict the spatiotemporal distribution of the population. We identified a unique systematic structure associated with their distribution in inclination and ascending node phase space. Given that HAMR objects are the most difficult to target from an observational point of view, this work will have many implications for the space surveillance community, and will allow observers to implement better search strategies for this class of debris.
Date of Conference: September 11-14, 2012
Track: Orbital Debris