Asteroids represent both an opportunity and a risk. Their pristine environment captures the early formation of the solar system; while their impact potential could result in the mass extinction of life. Amongst the many possibilities to deflect Near Earth Asteroids, laser ablation has been shown to be theoretically one of the most effective cases. However, to have full confidence in this approach current assumptions must be verified and fundamental questions answered. Current models assume that the asteroid’s body is a dense, non porous, homogenous structure. Forsterite is typically used to represent asteroids. However asteroids exist over an extended range of material compositions, initial rotational rates and surface features. Models must therefore be advanced to represent the diversity within the asteroid population. The nature, composition and geometry of the ejecta plume also requires accurate modelling. The affect of porosity on the expansion of the ejecta gas remains unknown. Existing models of contamination, particularly on the optical elements are limited to the rocket-engine equivalent model. Therefore to successfully assess the effectiveness and efficiency of the laser ablation technique a detailed understanding of each of these parameters is required. Supported by the Planetary Society and the Institute of Photonics, a series of self contained experiments were conducted that assessed the formation of the ejecta plume - gas, dust and other particles - and the rate of optical contamination for several different laser ablation events. This was a product of asteroid analogue target material(s) –dense, porous, and inhomogeneous -, surface geometry and laser beam characteristics. Each test occurred within a vacuum and was supported by a complementary in-situ monitoring system. High resolution, high speed cameras enabled reconstruction of the ejecta plume and flow field. Coupled with a thermal camera this enabled plume specific issues - geometry, ejection velocities, temperature profiles and the contamination flow to be examined. Highly polished mirrors were also used to collect the contaminated particles and assess the rate of degradation. This paper will therefore present the design & methodology, experimental considerations and results of the laser ablation experiments. All collected data has been compared against the theoretical prediction. This permitted the calibration of the current analytical modelling technique. Ultimately the experiment provided a detailed insight into the effectiveness of the laser system, and the laser ablation potential as a viable method of deflecting Near Earth Asteroids.

In this work we present the direct detection of radiation pressure on the Potentially Hazardous Asteroid 2009 BD, one of the smallest multi-opposition NEOs currently known, with H ~ 28.4.
Under the current purely gravitational model of NEODyS the object is considered a possible future impactor, with impact solutions starting in 2071. The object is too small to cause significant ground damage upon impact, but it is still an interesting test case to assess the relevance of radiation pressure on the NEO monitoring and impact prediction.

Our non-gravitational orbital determination is based on a large set of observations obtained by various stations during the discovery apparition, in early 2009, plus 6 additional high-accuracy astrometric positions obtained by us from Mauna Kea during two more oppositions in late 2009 and 2010.
Since this computation is extremely sensitive to the exact set of astrometric observations considered, it has also been necessary to devise accurate procedures to assess the quality of the data used in the solution (especially those from external sources), and possibly reject some outliers that may corrupt the accuracy of the results.

The detection of a radiation-related acceleration can be parameterized by adding a new fitted parameter to the orbital computation: the most physically reasonable choice is the Area to Mass Ratio (AMR) for the object, which is directly related to how the object reacts to the pressure from the incident light.
From the sparse photometry in the MPC astrometric dataset (averaged and debiased with a careful selection process) we can also derive a reasonably good estimate of the object’s absolute magnitude, that can be combined with the above-determined AMR to obtain a range of possible values for its average density (under some assumptions on shape and albedo).
The result is fully compatible with the object being of natural origin, and it is narrow enough to exclude a man-made nature.

The possible origin of this object, its future observability, and the importance of radiation pressure in the impact monitoring process, are also briefly discussed.

The Near Earth Object Mitigation Support System (NEOMiSS) is a decision support tool, enabling scientists, emergency planners and policy-makers to understand and assess the human vulnerability and risks due to a potential NEO collision with the Earth. NEOMiSS extends the functionality offered by the NEOSim and NEOimpactor tools, developed at the University of Southampton, with improved vulnerability models of multiple NEO impact hazards that also account for mass public evacuation. By using evacuation as a process to the vulnerability models it can be used as a vulnerability modifier, enabling NEOMiSS to deliver reliable predictions of the human casualties arising from impact hazards along a NEO risk corridor. As such, decisions affecting NEO deflection campaigns (which modify the risk corridor) can be taken in the context of the human consequences. In addition, NEOMiSS provides a mechanism for managing the uncertainties in the data and model-fitting, thereby enabling the confidence in risk assessments to be quantified.
Within NEOMiSS, the Comprehensive Econometric Micro-Simulator for Evacuations (CEMEvac) is used to calibrate a coarse-scale evacuation model that delivers evacuation flow-rate data for a variety of evacuation management strategies, cultural and social structures, across populated areas in the NEO risk corridor. CEMEvac, an agent-based evacuation simulator developed in collaboration with the University of Wisconsin-Madison, is based on evacuation behaviour studies conducted in the US and is able to model human travel behaviour both before and during an evacuation. The coarse-scale evacuation flow rates (or "evacuability" measures) provided in this manner, are subsequently used within the NEOMiSS vulnerability models to predict human casualties arising from individual NEO impact hazards.
This paper presents the results of a preliminary study using the NEOMiSS multi-hazard human vulnerability model. Here, NEOMiSS is used to predict the number of casualties arising from the impact of asteroid 99942 Apophis along the 2036 risk corridor.

In the present work we simulated the performances of different ground based networks of sensors. A wide survey is assumed to cover all the visible sky available during each night.
Three different scenarios for the network of sensors were considered:

Potentially Hazardous Asteroids (PHAs) are Near Earth Asteroids caraterised by a Minimum Orbital Intersection Distance (MOID) with Earth less to 0,05 A.U and an absolute magnitude H<22.
Those objects have sometimes a so significant close approach with Earth that they can be put on a chaotic orbit.
This kind of orbit is very sensitive for exemple to the initial conditions, to the planetary theory used (for instance JPL's model versus IMCCE's model) or even to the numerical integrator used (Lie Series, Bulirsch-Stoer or Radau).
New observations (optical, radar, fly-by or satellite mission) can improve those orbits and reduce the uncertainties on the Keplerian elements.

The Gaia mission is an astrometric mission that will be launched in 2012 and will observe a large number of Solar System Objects down to magnitude V≤20.
During the 5-year mission, Gaia will continuously scan the sky with a specific strategy: objects will be observed from two lines of sight separated with a constant basic angle. Five constants already fixed determinate the nominal scanning law of Gaia: The inertial spin rate (1°/min) that describe the rotation of the spacecraft around an axis perpendicular to those of the two fields of view, the solar-aspect angle (45°) that is the angle between the Sun and the spacecraft rotation axis, the precession period (63.12 days) which is the precession of the spin axis around the Sun-Earth direction. Two other constants are still free parameters: the initial spin phase, and the initial precession angle that will be fixed at the start of the nominal science operations. These latter are constraint by scientific outcome (e.g. possibility of performing test of fundamental physics) together with operational requirements (downlink to Earth windows). Several sets of observations of specific NEOs will hence be provided according to the initial precession angle.

The purpose here is to study the statistical impact of the initial precession angle on the error propagation and on the collision probability, especially for PHAs. We will also analyse the advantage of combining space-based to ground-based observation over long term, as well as in short term from observations in alert.

A major bottleneck in determining appropriate mitigation methods for Near-Earth Objects (NEOs) has been a lack of experimental data on the efficacy of each approach, forcing a reliance on simulations to determine mission effectiveness. As we move from the concept stage into true mission planning for effective NEO threat mitigation, we must depart from simulation of a few sample cases and instead use actual mission parameters to integrate modeling and simulation into the mission design cycle. This paper presents the development of simulation tools designed to be implemented as part of the mission design procedure for nuclear fragmentation and dispersion of an NEO. A description of the methods used will be presented, followed by a discussion of the advanced GPU (Graphics Processing Unit) computing technology applied to accelerate computation. Preliminary results of a fragmented NEO dispersion scenario are discussed, emphasizing global parameter search methods for use in engineering mission analysis.
A model of the NEO fragmentation process is presented under a subsurface nuclear explosion, contact burst, and standoff blast conditions. A Smoothed Particle Hydrodynamics (SPH) code is used to compare the results to past studies of nuclear shock propagation in brittle material and current research in hypervelocity impacts. This approach is contrasted to Arbitrary Lagrangian-Eulerian (ALE) codes in current use at the Lawrence Livermore National Laboratory for asteroid deflection simulation. We assume an isotropic Weibull distribution of implicit flaws in the NEO material and conduct Monte Carlo simulation to establish a mean response of the target NEO to the fragmentation process. Resulting coherent masses are propagated through a model of solar system dynamics until the predetermined date of impact. Masses remaining on impact trajectories undergo a simulation of reentry into Earth's atmosphere, resulting in final tallies of mass missing the Earth, fragments on capture trajectories, airburst events, and impacts of reduced-mass fragments. Past results show that, on some orbits, the impacting mass can be reduced to lower than 1% of the NEO mass. The present paper addresses multiple classes of orbits and NEO structures to provide guidelines for mission design analysis.
Historically, simulations have been limited to a few large test cases to demonstrate the viability of planetary defense options. This paper addresses the use of GPU computation, a new direction in high-performance computing (HPC), to achieve up to 150x faster computation in a workstation form factor. A dedicated compute server is shown to be 400x as fast as CPU implementation, and these are far cheaper than their HPC cluster and supercomputer counterparts. This has allowed for a revolution in computing on a budget, allowing hundreds of planetary defense simulations to be tested. While new HPC technology is shown to solve old problems faster, this paper also addresses the identification of new problems that were previously intractable without the use of a supercomputer. Specific performance and results from several GPU compute configurations will be presented.
Disruption of an NEO (i.e. fragmentation and dispersion) has been shown to be a viable option using current technology for some orbits. An extended characterization of disruption scenarios is discussed, and an effort is made to determine needed technological requirements for general nuclear disruption effectiveness. Improvements to fragmentation modeling, reentry modeling, and orbital dispersion modeling are presented. This paper outlines software and hardware tools that aid the development of NEO deflection mission design, and an ability to identify key technologies for effective implementation. We now have the technology and resources to move from threat to action, and a new era of planetary defense where we can focus on developing a standing threat mitigation capability is on the horizon.

The NEO population consists of those bodies having orbits which bring them "near" the earth. The bodies have semi major axes close to about 1 AU and aphelion or perihelion distances such that their orbits are earth crossing. The source of these objects is understood to be the main asteroid belt. Gravitational perturbation during close planetary encounters and the mean motion resonance with Jupiter causes these asteroids to jump over from the main asteroid belt to potentially Earth threatening orbits. Some of the NEOs like Enkhe are also of cometary origin. Though it appears that the collision possibility is remote, but the threat is as real, and is supported by both impact evidence (Tunguska 1908) and recent discoveries such as Aphopis (2004).
Smaller NEOs (<100 m) may burn up in the atmosphere during their descent while the approach of larger ones (>1 km) may be rare. It is the medium sized ones that pose the real threat. This is because they can cause extensive damage including mass extinctions and their probability is also significant. The detection of the NEOs should be given the highest priority. This is because the gravest danger is an undiscovered object impacting the planet and taking us by surprise. This represents a worrying gap in our knowledge about the NEOs.
The design process proposed in this paper mainly consists of (i) Numerical simulation of NEO objects (ii) Analysis of relative motion of objects with Earth (iii) Velocity impulse requirements to avoid collision. Prior information about the characteristics of the NEO like mass, size, shape, spin, centre of mass, orbital parameters and expected time of fly-by/impact are vital to the collision avoidance design process.
Given the orbital parameters and above mentioned characteristics of NEO which is likely to impact our planet (e.g. apophis), the author proposes to numerically propagate the orbit and check whether a NEO will collide with the earth or not. The author proposes to simulate using a numerical code based on appropriate integration schemes and an n body force model taking into account the sun, the planets and the Earth- moon system. The validation of the results would be done by comparing the results with standard/published results.
Once it is established that a collision is likely, the impulse required of successful deflection will be calculated to ensure a safe flyby distance by solving a Lambert problem involving the NEO object and Earth. This would include a comparative analysis of current conventional and advanced propulsion technologies.
The author proposes to do a conceptual mission design of a space craft using a suitable launcher in Indian context, which will attempt this deflection. Optimization studies to optimize the mass of the spacecraft, the impulse required and timing of the launch would form part of the exercise. The relative effectiveness of various deflection methods would also be explored. Use of moon’s gravity assist in deflecting the objects will be analyzed. Further, the possibility of colliding the object onto the moon will be explored as an active removal process.