Applications of Thermophysical Modelling to Near Earth Asteroids

Introduction: Asteroids illuminated by the Sun are in constant equilibrium between the absorbed solar radiation and the thermal radiation emitted from the asteroids themselves. The thermal flux is dependant on the surface temperature distribution of the asteroid, which in turn is dependant on several factors associated with the asteroid. These include heliocentric distance, albedo, orientation of the spin vector, rotation rate, global shape, and a number of thermal properties of the surface of which the thermal inertia is most important. Simple thermal models using idealised spherical geometry and idealised assumptions of the level of thermal inertia have previously been used to determine asteroid diameters and albedos when simultaneous measurements of disk-integrated asteroid flux have been made in the visible and infrared [1]. Although successful for determining diameters and albedos of main-belt asteroids, these models however, have obvious limitations when it comes to detailed interpretations from high quality spacecraft/observational data or for the prediction of accurate asteroid thermal infrared fluxes. This is especially true for near Earth asteroids where they are known to exhibit much more irregular shapes than main-belt asteroids. Thermophysical modelling is an attempt to account for all of the physical and thermal processes involved.