Modelling the IRAS solar system dust bands

The chief difficulties in interpreting the geometry of the IRAS solar system dust bands are (1) the geocentric viewpoint of the IRAS telescope and (2) the large range of elongation angles sampled by IRAS. To overcome these and other difficulties we have a constructed a three-dimensional numerical model that permits the calculation of the latitudinal distribution of the thermal flux that would be received at the Earth from any particular distribution of dust particle orbits. The model includes the effects of planetary perturbations on the dust particle orbits, reproduces the exact viewing geometry of the IRAS telescope, and allows for the eccentricity of the Earth's orbit. The result is a model for the variation with ecliptic latitude of the brightness observed in a given waveband as the line of sight of the telescope sweeps through the model dustband at a constant elongation angle. Models based on the Hirayama asteroid families are compared with the IRAS observations.