Yarkovsky effect on a body with variable albedo
Institute of Astronomy, Charles University, V Holešovičkách 2, 18000 Prague, Czech Republic e-mail: email@example.com
2 Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, USA
Accepted: 27 June 2006
Context.Precise observations and long orbital arcs make determining the orbit of small near-Earth asteroids a task of ever increasing difficulty. Subtle perturbations, such as relativistic terms or radiation forces, must be taken into account.
Aims.Vokrouhlický & Milani (2000) studied the orbital effects of radiation pressure on those spherical bodies with north-south asymmetry in taking the optical surface albedo value. However, their analysis omitted the complementary effect of recoil due to thermal radiation. Here we determine this component and study the degree of compensation between these two effects.
Methods.We use an analytic approach that requires linearization of the heat-diffusion boundary condition on the surface of the body and weakly eccentric orbits. We determine both diurnal and seasonal components of the thermal force due to albedo asymmetry, and we compute the related orbit-averaged change of the semimajor axis, eccentricity, and inclination.
Results.Within the limits of our approximation and with a plausible value of thermal parameters for small near-Earth asteroids, we show that the orbit-perturbation due to anisotropic reflection in the optical waveband is largely compensated by the anisotropic reflection in the thermal waveband. The resulting effect amounts to ~25% of the effect in the optical at maximum.
Key words: radiation mechanisms: thermal
© ESO, 2006