Mini-workshop: Studies results of the Ariadna Call for Ideas "Preparing for Apophis - Encounter 2029"
Future asteroid mitigation concepts and new tools to support future asteroid missions have been investigated by the Advanced Concepts Team together with universities. A workshop to present the results of the "Encounter 2029" Call for Ideas will take place on 3 April 2009 at ESTEC in meeting room Ef008. The three selected studies span from predicting asteroid trajectories to understanding asteroid fragmentation and innovative deflection techniques.
Near Earth Objects (NEOs) come closer to us than any other bodies in the solar system yet despite this, we still know relatively little about options to tackle the threat that they represent.
In 2029 the several-hundred-meter diameter asteroid 99942 Apophis (2004 MN4) will flyby the Earth at a distance of about 32 000 km. This is closer than any known past or future approach by natural objects larger than about 10 meters (other than objects that have entered Earth's atmosphere). After a resonant flyby, the asteroid will then return towards Earth with two potential impact dates between 2036 and 2037. Although it is known that Apophis will very likely not impact Earth on any of these dates, and while no NEO impact disastrous to society has occurred yet, the close encounter with Apophis in 2029 will provide a window of opportunity for scientific and technological research and for educating the public and decision makers on the nature of this recognized problem.
The main aim of this Call for Ideas was to attract proposals for new and innovative scientific and technical studies, which will act as the first steps towards increasing our knowledge.
Predicting asteroid trajectories using validated integrators and determining impact leading conditions (Politecnico di Milano)
Taylor model integrators have recently shown to be a powerful tool for the validated integration of ordinary differential equations. The study exploits these algorithms to rigorously predict the long-term motion of Near Earth Objects and the verified identification of impact occurrence. In particular, the first goal is to apply these techniques starting from a simple two-body problem up to a n-body dynamics including also relevant non-gravitational perturbations. By doing so, the validated integration of asteroids' motion can be addressed considering initial uncertainties consistent with the current measurement accuracies. In addition, an algorithm for the rigorous identification of impact-leading conditions has also been developed.
Determination of asteroid fragmentation energy from an impactor and post-fragmentation dynamics (Université de Nice Spohia-Antipolis)
A question often asked when addressing the problem of the deflection of a potential impactor is: how can we make sure that the projectile will deflect the asteroid instead of breaking it in large pieces? This is actually a fundamental problem of planetary science. It has become customary in the literature to characterize impacts in terms of a specific energy threshold (the kinetic energy in the collision divided by the target’s mass) that leads to a largest fragment containing 50% of the target’s original mass. The knowledge of this threshold as a function of the target’s properties, in particular its internal structure, is still a matter of intensive research and debates in the small body community. It is also fundamental because it is used in many studies, such as the collisional evolution of small body populations. For the first time, this study is addressing bodies with more complex internal structure (shattered, porous) where this threshold energy is proved to be well beyond the one that can be reasonably reached by an artificial projectile.
Mirror Bees concept for asteroid deflection (University of Glasgow)
This study analyzes the feasibility of a deflection concept based on the use of a number of mirrors (solar concentrators) to focus the solar energy onto a small portion of the surface of an asteroid. The resulting heat would sublimate the surface material creating a jet of gas and dust that would produce a continuous thrust. Among other parameters, this study assessed the influence of the asteroid properties, the required orbital and attitude control capabilities for each satellite and for the entire formation, and the system budget for each satellite in the formation.